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Atom | Electron cloud | Electron cloud
right|thumb|A potential well, showing, according to classical mechanics, the minimum energy V(x) needed to reach each position x. Classically, a particle with energy E is constrained to a range of positions between x1 and x2.
The electrons in an atom are attracted to the protons in the nucleus by the electromagnetic force. This force binds the electrons inside an electrostatic potential well surrounding the smaller nucleus, which means that an external source of energy is needed for the electron to escape. The closer an electron is to the nucleus, the greater the attractive force. Hence electrons bound near the center of the potential well require more energy to escape than those at greater separations.
Electrons, like other particles, have properties of both a particle and a wave. The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave—a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital, a mathematical function that characterises the probability that an electron appears to be at a particular location when its position is measured. Only a discrete (or quantized) set of these orbitals exist around the nucleus, as other possible wave patterns rapidly decay into a more stable form. Orbitals can have one or more ring or node structures, and differ from each other in size, shape and orientation.
thumb|upright=1.5|3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
Each atomic orbital corresponds to a particular energy level of the electron. The electron can change its state to a higher energy level by absorbing a photon with sufficient energy to boost it into the new quantum state. Likewise, through spontaneous emission, an electron in a higher energy state can drop to a lower energy state while radiating the excess energy as a photon. These characteristic energy values, defined by the differences in the energies of the quantum states, are responsible for atomic spectral lines.
The amount of energy needed to remove or add an electron—the electron binding energy—is far less than the binding energy of nucleons. For example, it requires only 13.6 eV to strip a ground-state electron from a hydrogen atom, compared to 2.23 million eV for splitting a deuterium nucleus. Atoms are electrically neutral if they have an equal number of protons and electrons. Atoms that have either a deficit or a surplus of electrons are called ions. Electrons that are farthest from the nucleus may be transferred to other nearby atoms or shared between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals. |
Atom | Properties | Properties |
Atom | Nuclear properties | Nuclear properties
By definition, any two atoms with an identical number of protons in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of neutrons are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The known elements form a set of atomic numbers, from the single-proton element hydrogen up to the 118-proton element oganesson. All known isotopes of elements with atomic numbers greater than 82 are radioactive, although the radioactivity of element 83 (bismuth) is so slight as to be practically negligible.
About 339 nuclides occur naturally on Earth, of which 251 (about 74%) have not been observed to decay, and are referred to as "stable isotopes". Only 90 nuclides are stable theoretically, while another 161 (bringing the total to 251) have not been observed to decay, even though in theory it is energetically possible. These are also formally classified as "stable". An additional 35 radioactive nuclides have half-lives longer than 100 million years, and are long-lived enough to have been present since the birth of the Solar System. This collection of 286 nuclides are known as primordial nuclides. Finally, an additional 53 short-lived nuclides are known to occur naturally, as daughter products of primordial nuclide decay (such as radium from uranium), or as products of natural energetic processes on Earth, such as cosmic ray bombardment (for example, carbon-14).For more recent updates see Brookhaven National Laboratory's Interactive Chart of Nuclides ] .
For 80 of the chemical elements, at least one stable isotope exists. As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.1 stable isotopes per element. Twenty-six "monoisotopic elements" have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes.CRC Handbook (2002).
Stability of isotopes is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These quantum shells correspond to a set of energy levels within the shell model of the nucleus; filled shells, such as the filled shell of 50 protons for tin, confers unusual stability on the nuclide. Of the 251 known stable nuclides, only four have both an odd number of protons and odd number of neutrons: hydrogen-2 (deuterium), lithium-6, boron-10, and nitrogen-14. (Tantalum-180m is odd-odd and observationally stable, but is predicted to decay with a very long half-life.) Also, only four naturally occurring, radioactive odd-odd nuclides have a half-life over a billion years: potassium-40, vanadium-50, lanthanum-138, and lutetium-176. Most odd-odd nuclei are highly unstable with respect to beta decay, because the decay products are even-even, and are therefore more strongly bound, due to nuclear pairing effects. |
Atom | Mass | Mass
The large majority of an atom's mass comes from the protons and neutrons that make it up. The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons).
The actual mass of an atom at rest is often expressed in daltons (Da), also called the unified atomic mass unit (u). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately . Hydrogen-1 (the lightest isotope of hydrogen which is also the nuclide with the lowest mass) has an atomic weight of 1.007825 Da. The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 Da), but this number will not be exactly an integer except (by definition) in the case of carbon-12. The heaviest stable atom is lead-208, with a mass of .
As even the most massive atoms are far too light to work with directly, chemists instead use the unit of moles. One mole of atoms of any element always has the same number of atoms (about ). This number was chosen so that if an element has an atomic mass of 1 u, a mole of atoms of that element has a mass close to one gram. Because of the definition of the unified atomic mass unit, each carbon-12 atom has an atomic mass of exactly 12 Da, and so a mole of carbon-12 atoms weighs exactly 0.012 kg. |
Atom | Shape and size | Shape and size
Atoms lack a well-defined outer boundary, so their dimensions are usually described in terms of an atomic radius. This is a measure of the distance out to which the electron cloud extends from the nucleus. This assumes the atom to exhibit a spherical shape, which is only obeyed for atoms in vacuum or free space. Atomic radii may be derived from the distances between two nuclei when the two atoms are joined in a chemical bond. The radius varies with the location of an atom on the atomic chart, the type of chemical bond, the number of neighboring atoms (coordination number) and a quantum mechanical property known as spin. On the periodic table of the elements, atom size tends to increase when moving down columns, but decrease when moving across rows (left to right). Consequently, the smallest atom is helium with a radius of 32 pm, while one of the largest is caesium at 225 pm.
When subjected to external forces, like electrical fields, the shape of an atom may deviate from spherical symmetry. The deformation depends on the field magnitude and the orbital type of outer shell electrons, as shown by group-theoretical considerations. Aspherical deviations might be elicited for instance in crystals, where large crystal-electrical fields may occur at low-symmetry lattice sites. Significant ellipsoidal deformations have been shown to occur for sulfur ions and chalcogen ions in pyrite-type compounds.
Atomic dimensions are thousands of times smaller than the wavelengths of light (400–700 nm) so they cannot be viewed using an optical microscope, although individual atoms can be observed using a scanning tunneling microscope. To visualize the minuteness of the atom, consider that a typical human hair is about 1 million carbon atoms in width. A single drop of water contains about 2 sextillion () atoms of oxygen, and twice the number of hydrogen atoms. A single carat diamond with a mass of contains about 10 sextillion (1022) atoms of carbon.A carat is 200 milligrams. By definition, carbon-12 has 0.012 kg per mole. The Avogadro constant defines atoms per mole. If an apple were magnified to the size of the Earth, then the atoms in the apple would be approximately the size of the original apple. |
Atom | Radioactive decay | Radioactive decay
right|thumb|This diagram shows the half-life (T) of various isotopes with Z protons and N neutrons.
Every element has one or more isotopes that have unstable nuclei that are subject to radioactive decay, causing the nucleus to emit particles or electromagnetic radiation. Radioactivity can occur when the radius of a nucleus is large compared with the radius of the strong force, which only acts over distances on the order of 1 fm.
The most common forms of radioactive decay are:
Alpha decay: this process is caused when the nucleus emits an alpha particle, which is a helium nucleus consisting of two protons and two neutrons. The result of the emission is a new element with a lower atomic number.
Beta decay (and electron capture): these processes are regulated by the weak force, and result from a transformation of a neutron into a proton, or a proton into a neutron. The neutron to proton transition is accompanied by the emission of an electron and an antineutrino, while proton to neutron transition (except in electron capture) causes the emission of a positron and a neutrino. The electron or positron emissions are called beta particles. Beta decay either increases or decreases the atomic number of the nucleus by one. Electron capture is more common than positron emission, because it requires less energy. In this type of decay, an electron is absorbed by the nucleus, rather than a positron emitted from the nucleus. A neutrino is still emitted in this process, and a proton changes to a neutron.
Gamma decay: this process results from a change in the energy level of the nucleus to a lower state, resulting in the emission of electromagnetic radiation. The excited state of a nucleus which results in gamma emission usually occurs following the emission of an alpha or a beta particle. Thus, gamma decay usually follows alpha or beta decay.
Other more rare types of radioactive decay include ejection of neutrons or protons or clusters of nucleons from a nucleus, or more than one beta particle. An analog of gamma emission which allows excited nuclei to lose energy in a different way, is internal conversion—a process that produces high-speed electrons that are not beta rays, followed by production of high-energy photons that are not gamma rays. A few large nuclei explode into two or more charged fragments of varying masses plus several neutrons, in a decay called spontaneous nuclear fission.
Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth. |
Atom | Magnetic moment | Magnetic moment
Elementary particles possess an intrinsic quantum mechanical property known as spin. This is analogous to the angular momentum of an object that is spinning around its center of mass, although strictly speaking these particles are believed to be point-like and cannot be said to be rotating. Spin is measured in units of the reduced Planck constant (ħ), with electrons, protons and neutrons all having spin ħ, or "spin-". In an atom, electrons in motion around the nucleus possess orbital angular momentum in addition to their spin, while the nucleus itself possesses angular momentum due to its nuclear spin.
The magnetic field produced by an atom—its magnetic moment—is determined by these various forms of angular momentum, just as a rotating charged object classically produces a magnetic field, but the most dominant contribution comes from electron spin. Due to the nature of electrons to obey the Pauli exclusion principle, in which no two electrons may be found in the same quantum state, bound electrons pair up with each other, with one member of each pair in a spin up state and the other in the opposite, spin down state. Thus these spins cancel each other out, reducing the total magnetic dipole moment to zero in some atoms with even number of electrons.
In ferromagnetic elements such as iron, cobalt and nickel, an odd number of electrons leads to an unpaired electron and a net overall magnetic moment. The orbitals of neighboring atoms overlap and a lower energy state is achieved when the spins of unpaired electrons are aligned with each other, a spontaneous process known as an exchange interaction. When the magnetic moments of ferromagnetic atoms are lined up, the material can produce a measurable macroscopic field. Paramagnetic materials have atoms with magnetic moments that line up in random directions when no magnetic field is present, but the magnetic moments of the individual atoms line up in the presence of a field.
The nucleus of an atom will have no spin when it has even numbers of both neutrons and protons, but for other cases of odd numbers, the nucleus may have a spin. Normally nuclei with spin are aligned in random directions because of thermal equilibrium, but for certain elements (such as xenon-129) it is possible to polarize a significant proportion of the nuclear spin states so that they are aligned in the same direction—a condition called hyperpolarization. This has important applications in magnetic resonance imaging. |
Atom | Energy levels | Energy levels
thumb|right|These electron's energy levels (not to scale) are sufficient for ground states of atoms up to cadmium (5s2 4d10) inclusively. The top of the diagram is lower than an unbound electron state.
The potential energy of an electron in an atom is negative relative to when the distance from the nucleus goes to infinity; its dependence on the electron's position reaches the minimum inside the nucleus, roughly in inverse proportion to the distance. In the quantum-mechanical model, a bound electron can occupy only a set of states centered on the nucleus, and each state corresponds to a specific energy level; see time-independent Schrödinger equation for a theoretical explanation. An energy level can be measured by the amount of energy needed to unbind the electron from the atom, and is usually given in units of electronvolts (eV). The lowest energy state of a bound electron is called the ground state, i.e., stationary state, while an electron transition to a higher level results in an excited state. The electron's energy increases along with n because the (average) distance to the nucleus increases. Dependence of the energy on is caused not by the electrostatic potential of the nucleus, but by interaction between electrons.
For an electron to transition between two different states, e.g. ground state to first excited state, it must absorb or emit a photon at an energy matching the difference in the potential energy of those levels, according to the Niels Bohr model, what can be precisely calculated by the Schrödinger equation. Electrons jump between orbitals in a particle-like fashion. For example, if a single photon strikes the electrons, only a single electron changes states in response to the photon; see Electron properties.
The energy of an emitted photon is proportional to its frequency, so these specific energy levels appear as distinct bands in the electromagnetic spectrum. Each element has a characteristic spectrum that can depend on the nuclear charge, subshells filled by electrons, the electromagnetic interactions between the electrons and other factors.
right|thumb|upright=1.5|An example of absorption lines in a spectrum
When a continuous spectrum of energy is passed through a gas or plasma, some of the photons are absorbed by atoms, causing electrons to change their energy level. Those excited electrons that remain bound to their atom spontaneously emit this energy as a photon, traveling in a random direction, and so drop back to lower energy levels. Thus the atoms behave like a filter that forms a series of dark absorption bands in the energy output. (An observer viewing the atoms from a view that does not include the continuous spectrum in the background, instead sees a series of emission lines from the photons emitted by the atoms.) Spectroscopic measurements of the strength and width of atomic spectral lines allow the composition and physical properties of a substance to be determined.
Close examination of the spectral lines reveals that some display a fine structure splitting. This occurs because of spin–orbit coupling, which is an interaction between the spin and motion of the outermost electron. When an atom is in an external magnetic field, spectral lines become split into three or more components; a phenomenon called the Zeeman effect. This is caused by the interaction of the magnetic field with the magnetic moment of the atom and its electrons. Some atoms can have multiple electron configurations with the same energy level, which thus appear as a single spectral line. The interaction of the magnetic field with the atom shifts these electron configurations to slightly different energy levels, resulting in multiple spectral lines. The presence of an external electric field can cause a comparable splitting and shifting of spectral lines by modifying the electron energy levels, a phenomenon called the Stark effect.
If a bound electron is in an excited state, an interacting photon with the proper energy can cause stimulated emission of a photon with a matching energy level. For this to occur, the electron must drop to a lower energy state that has an energy difference matching the energy of the interacting photon. The emitted photon and the interacting photon then move off in parallel and with matching phases. That is, the wave patterns of the two photons are synchronized. This physical property is used to make lasers, which can emit a coherent beam of light energy in a narrow frequency band. |
Atom | Valence and bonding behavior | Valence and bonding behavior
Valency is the combining power of an element. It is determined by the number of bonds it can form to other atoms or groups. The outermost electron shell of an atom in its uncombined state is known as the valence shell, and the electrons in
that shell are called valence electrons. The number of valence electrons determines the bonding
behavior with other atoms. Atoms tend to chemically react with each other in a manner that fills (or empties) their outer valence shells. For example, a transfer of a single electron between atoms is a useful approximation for bonds that form between atoms with one-electron more than a filled shell, and others that are one-electron short of a full shell, such as occurs in the compound sodium chloride and other chemical ionic salts. Many elements display multiple valences, or tendencies to share differing numbers of electrons in different compounds. Thus, chemical bonding between these elements takes many forms of electron-sharing that are more than simple electron transfers. Examples include the element carbon and the organic compounds.
The chemical elements are often displayed in a periodic table that is laid out to display recurring chemical properties, and elements with the same number of valence electrons form a group that is aligned in the same column of the table. (The horizontal rows correspond to the filling of a quantum shell of electrons.) The elements at the far right of the table have their outer shell completely filled with electrons, which results in chemically inert elements known as the noble gases. |
Atom | States | States
right|thumb|Graphic illustrating the formation of a Bose–Einstein condensate
Quantities of atoms are found in different states of matter that depend on the physical conditions, such as temperature and pressure. By varying the conditions, materials can transition between solids, liquids, gases, and plasmas. Within a state, a material can also exist in different allotropes. An example of this is solid carbon, which can exist as graphite or diamond. Gaseous allotropes exist as well, such as dioxygen and ozone.
At temperatures close to absolute zero, atoms can form a Bose–Einstein condensate, at which point quantum mechanical effects, which are normally only observed at the atomic scale, become apparent on a macroscopic scale. This super-cooled collection of atoms then behaves as a single super atom, which may allow fundamental checks of quantum mechanical behavior. |
Atom | Identification | Identification
right|thumb|Scanning tunneling microscope surface reconstruction image showing the individual atoms making up this gold (100) surface. The surface atoms deviate from the bulk crystal structure and arrange in columns several atoms wide with pits between them.
While atoms are too small to be seen, devices such as the scanning tunneling microscope (STM) enable their visualization at the surfaces of solids. The microscope uses the quantum tunneling phenomenon, which allows particles to pass through a barrier that would be insurmountable in the classical perspective. Electrons tunnel through the vacuum between two biased electrodes, providing a tunneling current that is exponentially dependent on their separation. One electrode is a sharp tip ideally ending with a single atom. At each point of the scan of the surface the tip's height is adjusted so as to keep the tunneling current at a set value. How much the tip moves to and away from the surface is interpreted as the height profile. For low bias, the microscope images the averaged electron orbitals across closely packed energy levels—the local density of the electronic states near the Fermi level. Because of the distances involved, both electrodes need to be extremely stable; only then periodicities can be observed that correspond to individual atoms. The method alone is not chemically specific, and cannot identify the atomic species present at the surface.
Atoms can be easily identified by their mass. If an atom is ionized by removing one of its electrons, its trajectory when it passes through a magnetic field will bend. The radius by which the trajectory of a moving ion is turned by the magnetic field is determined by the mass of the atom. The mass spectrometer uses this principle to measure the mass-to-charge ratio of ions. If a sample contains multiple isotopes, the mass spectrometer can determine the proportion of each isotope in the sample by measuring the intensity of the different beams of ions. Techniques to vaporize atoms include inductively coupled plasma atomic emission spectroscopy and inductively coupled plasma mass spectrometry, both of which use a plasma to vaporize samples for analysis.
The atom-probe tomograph has sub-nanometer resolution in 3-D and can chemically identify individual atoms using time-of-flight mass spectrometry.
Electron emission techniques such as X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), which measure the binding energies of the core electrons, are used to identify the atomic species present in a sample in a non-destructive way. With proper focusing both can be made area-specific. Another such method is electron energy loss spectroscopy (EELS), which measures the energy loss of an electron beam within a transmission electron microscope when it interacts with a portion of a sample.
Spectra of excited states can be used to analyze the atomic composition of distant stars. Specific light wavelengths contained in the observed light from stars can be separated out and related to the quantized transitions in free gas atoms. These colors can be replicated using a gas-discharge lamp containing the same element. Helium was discovered in this way in the spectrum of the Sun 23 years before it was found on Earth. |
Atom | Origin and current state | Origin and current state
Baryonic matter forms about 4% of the total energy density of the observable universe, with an average density of about 0.25 particles/m3 (mostly protons and electrons). Within a galaxy such as the Milky Way, particles have a much higher concentration, with the density of matter in the interstellar medium (ISM) ranging from 105 to 109 atoms/m3. The Sun is believed to be inside the Local Bubble, so the density in the solar neighborhood is only about 103 atoms/m3. Stars form from dense clouds in the ISM, and the evolutionary processes of stars result in the steady enrichment of the ISM with elements more massive than hydrogen and helium.
Up to 95% of the Milky Way's baryonic matter are concentrated inside stars, where conditions are unfavorable for atomic matter. The total baryonic mass is about 10% of the mass of the galaxy; the remainder of the mass is an unknown dark matter. High temperature inside stars makes most "atoms" fully ionized, that is, separates all electrons from the nuclei. In stellar remnants—with exception of their surface layers—an immense pressure make electron shells impossible. |
Atom | Formation | Formation
thumb|600px|Periodic table showing the origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process). Elements heavier than iron may be made in neutron star mergers or supernovae after the r-process.
Electrons are thought to exist in the Universe since early stages of the Big Bang. Atomic nuclei forms in nucleosynthesis reactions. In about three minutes Big Bang nucleosynthesis produced most of the helium, lithium, and deuterium in the Universe, and perhaps some of the beryllium and boron.
Ubiquitousness and stability of atoms relies on their binding energy, which means that an atom has a lower energy than an unbound system of the nucleus and electrons. Where the temperature is much higher than ionization potential, the matter exists in the form of plasma—a gas of positively charged ions (possibly, bare nuclei) and electrons. When the temperature drops below the ionization potential, atoms become statistically favorable. Atoms (complete with bound electrons) became to dominate over charged particles 380,000 years after the Big Bang—an epoch called recombination, when the expanding Universe cooled enough to allow electrons to become attached to nuclei.
Since the Big Bang, which produced no carbon or heavier elements, atomic nuclei have been combined in stars through the process of nuclear fusion to produce more of the element helium, and (via the triple-alpha process) the sequence of elements from carbon up to iron; see stellar nucleosynthesis for details.
Isotopes such as lithium-6, as well as some beryllium and boron are generated in space through cosmic ray spallation. This occurs when a high-energy proton strikes an atomic nucleus, causing large numbers of nucleons to be ejected.
Elements heavier than iron were produced in supernovae and colliding neutron stars through the r-process, and in AGB stars through the s-process, both of which involve the capture of neutrons by atomic nuclei. Elements such as lead formed largely through the radioactive decay of heavier elements. |
Atom | Earth | Earth
Most of the atoms that make up the Earth and its inhabitants were present in their current form in the nebula that collapsed out of a molecular cloud to form the Solar System. The rest are the result of radioactive decay, and their relative proportion can be used to determine the age of the Earth through radiometric dating.Manuel (2001). Origin of Elements in the Solar System, pp. 40–430, 511–519 Most of the helium in the crust of the Earth (about 99% of the helium from gas wells, as shown by its lower abundance of helium-3) is a product of alpha decay.
There are a few trace atoms on Earth that were not present at the beginning (i.e., not "primordial"), nor are results of radioactive decay. Carbon-14 is continuously generated by cosmic rays in the atmosphere. Some atoms on Earth have been artificially generated either deliberately or as by-products of nuclear reactors or explosions. Of the transuranic elements—those with atomic numbers greater than 92—only plutonium and neptunium occur naturally on Earth. Transuranic elements have radioactive lifetimes shorter than the current age of the Earth and thus identifiable quantities of these elements have long since decayed, with the exception of traces of plutonium-244 possibly deposited by cosmic dust. Natural deposits of plutonium and neptunium are produced by neutron capture in uranium ore.
The Earth contains approximately atoms. Although small numbers of independent atoms of noble gases exist, such as argon, neon, and helium, 99% of the atmosphere is bound in the form of molecules, including carbon dioxide and diatomic oxygen and nitrogen. At the surface of the Earth, an overwhelming majority of atoms combine to form various compounds, including water, salt, silicates, and oxides. Atoms can also combine to create materials that do not consist of discrete molecules, including crystals and liquid or solid metals. This atomic matter forms networked arrangements that lack the particular type of small-scale interrupted order associated with molecular matter. |
Atom | Rare and theoretical forms | Rare and theoretical forms |
Atom | Superheavy elements | Superheavy elements
All nuclides with atomic numbers higher than 82 (lead) are known to be radioactive. No nuclide with an atomic number exceeding 92 (uranium) exists on Earth as a primordial nuclide, and heavier elements generally have shorter half-lives. Nevertheless, an "island of stability" encompassing relatively long-lived isotopes of superheavy elements with atomic numbers 110 to 114 might exist. Predictions for the half-life of the most stable nuclide on the island range from a few minutes to millions of years. In any case, superheavy elements (with Z > 104) would not exist due to increasing Coulomb repulsion (which results in spontaneous fission with increasingly short half-lives) in the absence of any stabilizing effects. |
Atom | Exotic matter | Exotic matter
Each particle of matter has a corresponding antimatter particle with the opposite electrical charge. Thus, the positron is a positively charged antielectron and the antiproton is a negatively charged equivalent of a proton. When a matter and corresponding antimatter particle meet, they annihilate each other. Because of this, along with an imbalance between the number of matter and antimatter particles, the latter are rare in the universe. The first causes of this imbalance are not yet fully understood, although theories of baryogenesis may offer an explanation. As a result, no antimatter atoms have been discovered in nature. In 1996, the antimatter counterpart of the hydrogen atom (antihydrogen) was synthesized at the CERN laboratory in Geneva.
Other exotic atoms have been created by replacing one of the protons, neutrons or electrons with other particles that have the same charge. For example, an electron can be replaced by a more massive muon, forming a muonic atom. These types of atoms can be used to test fundamental predictions of physics. |
Atom | See also | See also |
Atom | Notes | Notes |
Atom | References | References |
Atom | Bibliography | Bibliography
|
Atom | Further reading | Further reading
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Atom | External links | External links
Atoms in Motion – The Feynman Lectures on Physics
Category:Chemistry
Category:Articles containing video clips |
Atom | Table of Content | Short description, History of atomic theory, In philosophy, Dalton's law of multiple proportions, Discovery of the electron, Discovery of the nucleus, Bohr model, Discovery of protons and neutrons, The current consensus model, Structure, Subatomic particles, Nucleus, Electron cloud, Properties, Nuclear properties, Mass, Shape and size, Radioactive decay, Magnetic moment, Energy levels, Valence and bonding behavior, States, Identification, Origin and current state, Formation, Earth, Rare and theoretical forms, Superheavy elements, Exotic matter, See also, Notes, References, Bibliography, Further reading, External links |
Arable land | short description | upright=1.25|thumb| Modern mechanised agriculture permits large fields like this one in Dorset, England
Arable land (from the , "able to be ploughed") is any land capable of being ploughed and used to grow crops.Oxford English Dictionary, "arable, adj. and n." Oxford University Press (Oxford), 2013. Alternatively, for the purposes of agricultural statistics,The World Bank. Agricultural land (% of land area) http://data.worldbank.org/indicator/AG.LND.AGRI.ZS the term often has a more precise definition:
A more concise definition appearing in the Eurostat glossary similarly refers to actual rather than potential uses: "land worked (ploughed or tilled) regularly, generally under a system of crop rotation".Eurostat. Glossary: Arable land. http://ec.europa.eu/eurostat/statistics-explained/index.php/Glossary:Arable_land In Britain, arable land has traditionally been contrasted with pasturable land such as heaths, which could be used for sheep-rearing but not as farmland.
Arable land is vulnerable to land degradation and some types of un-arable land can be enriched to create useful land. Climate change and biodiversity loss are driving pressure on arable land. https://www.ipcc.ch/report/srccl/. |
Arable land | By country | By country
thumb|upright=1.8|Share of land area used for arable agriculture, OWID
According to the Food and Agriculture Organization of the United Nations, in 2013, the world's arable land amounted to 1.407 billion hectares, out of a total of 4.924 billion hectares of land used for agriculture.
+ Arable land area (1000 ha) Rank Country or region 2015 2016 2017 2018 2019 1 156,645 157,191 157,737 157,737 157,737 2 156,413 156,317 156,317 156,317 156,067 3 121,649 121,649 121,649 121,649 121,649 4 119,593 119,512 119,477 119,475 119,474 5 54,518 55,140 55,762 55,762 55,762 6 38,282 38,530 38,509 38,690 38,648 7 34,000 34,000 34,000 34,000 34,000 8 32,775 32,776 32,773 32,889 32,924 9 36,688 35,337 33,985 32,633 32,633 10 31,090 30,057 30,752 30,974 30,573 |
Arable land | Arable land (hectares per person) | Arable land (hectares per person)
upright=1.35|thumb|Fields in the region of Záhorie in Western Slovakia
thumb|right|upright=1.35|A field of sunflowers in Cardejón, Spain
+ Country Name 2013 Afghanistan 0.254 Albania 0.213 Algeria 0.196 American Samoa 0.054 Andorra 0.038 Angola 0.209 Antigua and Barbuda 0.044 Argentina 0.933 Armenia 0.150 Aruba 0.019 Australia 1.999 Austria 0.160 Azerbaijan 0.204 Bahamas, The 0.021 Bahrain 0.001 Bangladesh 0.049 Barbados 0.039 Belarus 0.589 Belgium 0.073 Belize 0.227 Benin 0.262 Bermuda 0.005 Bhutan 0.133 Bolivia 0.427 Bosnia and Herzegovina 0.264 Botswana 0.125 Brazil 0.372 British Virgin Islands 0.034 Brunei Darussalam 0.012 Bulgaria 0.479 Burkina Faso 0.363 Burundi 0.115 Cabo Verde 0.108 Cambodia 0.275 Cameroon 0.279 Canada 1.306 Cayman Islands 0.003 Central African Republic 0.382 Chad 0.373 Channel Islands 0.026 Chile 0.074 China 0.078 Colombia 0.036 Comoros 0.086 Congo, Dem. Rep. 0.098 Congo, Rep. 0.125 Costa Rica 0.049 Côte d'Ivoire 0.134 Croatia 0.206 Cuba 0.278 Curaçao Cyprus 0.070 Czech Republic 0.299 Denmark 0.429 Djibouti 0.002 Dominica 0.083 Dominican Republic 0.078 Ecuador 0.076 Egypt, Arab Rep. 0.031 El Salvador 0.120 Equatorial Guinea 0.151 Eritrea Estonia 0.480 Ethiopia 0.160 Faroe Islands 0.062 Fiji 0.187 Finland 0.409 France 0.277 French Polynesia 0.009 Gabon 0.197 Gambia, The 0.236 Georgia 0.119 Germany 0.145 Ghana 0.180 Gibraltar Greece 0.232 Greenland 0.016 Grenada 0.028 Guam 0.006 Guatemala 0.064 Guinea 0.259 Guinea-Bissau 0.171 Guyana 0.552 Haiti 0.103 Honduras 0.130 Hong Kong SAR, China 0.000 Hungary 0.445 Iceland 0.374 India 0.123 Indonesia 0.094 Iran, Islamic Rep. 0.193 Iraq 0.147 Ireland 0.242 Isle of Man 0.253 Israel 0.035 Italy 0.113 Jamaica 0.044 Japan 0.033 Jordan 0.032 Kazakhstan 1.726 Kenya 0.133 Kiribati 0.018 Korea, Dem. People's Rep. 0.094 Korea, Rep. 0.030 Kosovo Kuwait 0.003 Kyrgyz Republic 0.223 Lao PDR 0.226 Latvia 0.600 Lebanon 0.025 Lesotho 0.119 Liberia 0.116 Libya 0.274 Liechtenstein 0.070 Lithuania 0.774 Luxembourg 0.115 Macao SAR, China Macedonia, FYR 0.199 Madagascar 0.153 Malawi 0.235 Malaysia 0.032 Maldives 0.010 Mali 0.386 Malta 0.021 Marshall Islands 0.038 Mauritania 0.116 Mauritius 0.060 Mexico 0.186 Micronesia, Fed. Sts. 0.019 Moldova 0.510 Monaco Mongolia 0.198 Montenegro 0.013 Morocco 0.240 Mozambique 0.213 Myanmar 0.203 Namibia 0.341 Nauru Nepal 0.076 Netherlands 0.062 New Caledonia 0.024 New Zealand 0.123 Nicaragua 0.253 Niger 0.866 Nigeria 0.197 Northern Mariana Islands 0.019 Norway 0.159 Oman 0.010 Pakistan 0.168 Palau 0.048 Panama 0.148 Papua New Guinea 0.041 Paraguay 0.696 Peru 0.136 Philippines 0.057 Poland 0.284 Portugal 0.107 Puerto Rico 0.017 Qatar 0.007 Romania 0.438 Russian Federation 0.852 Rwanda 0.107 Samoa 0.042 San Marino 0.032 São Tomé and Príncipe 0.048 Saudi Arabia 0.102 Senegal 0.229 Serbia 0.460 Seychelles 0.001 Sierra Leone 0.256 Singapore 0.000 Sint Maarten (Dutch part) Slovak Republic 0.258 Slovenia 0.085 Solomon Islands 0.036 Somalia 0.107 South Africa 0.235 South Sudan Spain 0.270 Sri Lanka 0.063 St. Kitts and Nevis 0.092 St. Lucia 0.016 St. Martin (French part) St. Vincent and the Grenadines 0.046 Sudan 0.345 Suriname 0.112 Swaziland 0.140 Sweden 0.270 Switzerland 0.050 Syrian Arab Republic 0.241 Tajikistan 0.106 Tanzania 0.269 Thailand 0.249 Timor-Leste 0.131 Togo 0.382 Tonga 0.152 Trinidad and Tobago 0.019 Tunisia 0.262 Turkey 0.270 Turkmenistan 0.370 Turks and Caicos Islands 0.030 Tuvalu Uganda 0.189 Ukraine 0.715 United Arab Emirates 0.004 United Kingdom 0.098 United States 0.480 Uruguay 0.682 Uzbekistan 0.145 Vanuatu 0.079 Venezuela, RB 0.089 Vietnam 0.071 Virgin Islands (US) 0.010 West Bank and Gaza 0.011 Yemen, Rep. 0.049 Zambia 0.243 Zimbabwe 0.268 |
Arable land | Non-arable land | Non-arable land
thumb|upright=1.25|Water buffalo ploughing rice fields near Salatiga, Central Java, Indonesia
thumb|upright=1.25|A pasture in the East Riding of Yorkshire in England
Agricultural land that is not arable according to the FAO definition above includes:
Meadows and pasturesland used as pasture and grazed range, and those natural grasslands and sedge meadows that are used for hay production in some regions.
Permanent cropland that produces crops from woody vegetation, e.g. orchard land, vineyards, coffee plantations, rubber plantations, and land producing nut trees;
Other non-arable land includes land that is not suitable for any agricultural use. Land that is not arable, in the sense of lacking capability or suitability for cultivation for crop production, has one or more limitationsa lack of sufficient freshwater for irrigation, stoniness, steepness, adverse climate, excessive wetness with the impracticality of drainage, excessive salts, or a combination of these, among others.United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. Agriculture Handbook 210. 21 pp. Although such limitations may preclude cultivation, and some will in some cases preclude any agricultural use, large areas unsuitable for cultivation may still be agriculturally productive. For example, United States NRCS statistics indicate that about 59 percent of US non-federal pasture and unforested rangeland is unsuitable for cultivation, yet such land has value for grazing of livestock.NRCS. 2013. Summary report 2010 national resources inventory. The United States Natural Resources Conservation Service. 163 pp. In British Columbia, Canada, 41 percent of the provincial Agricultural Land Reserve area is unsuitable for the production of cultivated crops, but is suitable for uncultivated production of forage usable by grazing livestock.Agricultural Land Commission. Agriculture Capability and the ALR Fact Sheet. http://www.alc.gov.bc.ca/alc/DownloadAsset?assetId=72876D8604EC45279B8D3C1B14428CF8&filename=agriculture_capability__the_alr_fact_sheet_2013.pdf Similar examples can be found in many rangeland areas elsewhere. |
Arable land | Changes in arability | Changes in arability |
Arable land | Land conversion | Land conversion
Land incapable of being cultivated for the production of crops can sometimes be converted to arable land. New arable land makes more food and can reduce starvation. This outcome also makes a country more self-sufficient and politically independent, because food importation is reduced. Making non-arable land arable often involves digging new irrigation canals and new wells, aqueducts, desalination plants, planting trees for shade in the desert, hydroponics, fertilizer, nitrogen fertilizer, pesticides, reverse osmosis water processors, PET film insulation or other insulation against heat and cold, digging ditches and hills for protection against the wind, and installing greenhouses with internal light and heat for protection against the cold outside and to provide light in cloudy areas. Such modifications are often prohibitively expensive. An alternative is the seawater greenhouse, which desalinates water through evaporation and condensation using solar energy as the only energy input. This technology is optimized to grow crops on desert land close to the sea.
The use of artifices does not make the land arable. Rock still remains rock, and shallowless than turnable soil is still not considered toilable. The use of artifice is an open-air non-recycled water hydroponics relationship. The below described circumstances are not in perspective, have limited duration, and have a tendency to accumulate trace materials in soil that either there or elsewhere cause deoxygenation. The use of vast amounts of fertilizer may have unintended consequences for the environment by devastating rivers, waterways, and river endings through the accumulation of non-degradable toxins and nitrogen-bearing molecules that remove oxygen and cause non-aerobic processes to form.
Examples of infertile non-arable land being turned into fertile arable land include:
Aran Islands: These islands off the west coast of Ireland (not to be confused with the Isle of Arran in Scotland's Firth of Clyde) were unsuitable for arable farming because they were too rocky. The people covered the islands with a shallow layer of seaweed and sand from the ocean. Today, crops are grown there, even though the islands are still considered non-arable.
Israel: The construction of desalination plants along Israel's coast allowed agriculture in some areas that were formerly desert. The desalination plants, which remove the salt from ocean water, have produced a new source of water for farming, drinking, and washing.
Slash and burn agriculture uses nutrients from the wood ash, but these are exhausted within a few years.
Terra preta, fertile tropical soils produced by adding charcoal. |
Arable land | Land degradation | Land degradation |
Arable land | Examples | Examples
Examples of fertile arable land being turned into infertile land include:
Droughts such as the "Dust Bowl" of the Great Depression in the US turned farmland into desert.
Each year, arable land is lost due to desertification and human-induced erosion. Improper irrigation of farmland can wick the sodium, calcium, and magnesium from the soil and water to the surface. This process steadily concentrates salt in the root zone, decreasing productivity for crops that are not salt-tolerant.
Rainforest deforestation: The fertile tropical forests are converted into infertile desert land. For example, Madagascar's central highland plateau has become virtually totally barren (about ten percent of the country) as a result of slash-and-burn deforestation, an element of shifting cultivation practiced by many natives. |
Arable land | See also | See also
Development easement
Land use statistics by country
List of environment topics
Soil fertility |
Arable land | References | References |
Arable land | External links | External links
Article from Technorati on Shrinking Arable Farmland in the world
Surface area of the Earth
Category:Agricultural land |
Arable land | Table of Content | short description, By country, Arable land (hectares per person), Non-arable land, Changes in arability, Land conversion, Land degradation, Examples, See also, References, External links |
Aluminium | other uses | Aluminium (or aluminum in North American English) is a chemical element; it has symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has a great affinity towards oxygen, forming a protective layer of oxide on the surface when exposed to air. It visually resembles silver, both in its color and in its great ability to reflect light. It is soft, nonmagnetic, and ductile. It has one stable isotope, 27Al, which is highly abundant, making aluminium the 12th-most abundant element in the universe. The radioactivity of 26Al leads to it being used in radiometric dating.
Chemically, aluminium is a post-transition metal in the boron group; as is common for the group, aluminium forms compounds primarily in the +3 oxidation state. The aluminium cation Al3+ is small and highly charged; as such, it has more polarizing power, and bonds formed by aluminium have a more covalent character. The strong affinity of aluminium for oxygen leads to the common occurrence of its oxides in nature. Aluminium is found on Earth primarily in rocks in the crust, where it is the third-most abundant element, after oxygen and silicon, rather than in the mantle, and virtually never as the free metal. It is obtained industrially by mining bauxite, a sedimentary rock rich in aluminium minerals.
The discovery of aluminium was announced in 1825 by Danish physicist Hans Christian Ørsted. The first industrial production of aluminium was initiated by French chemist Henri Étienne Sainte-Claire Deville in 1856. Aluminium became much more available to the public with the Hall–Héroult process developed independently by French engineer Paul Héroult and American engineer Charles Martin Hall in 1886, and the mass production of aluminium led to its extensive use in industry and everyday life. In the First and Second World Wars, aluminium was a crucial strategic resource for aviation. In 1954, aluminium became the most produced non-ferrous metal, surpassing copper. In the 21st century, most aluminium was consumed in transportation, engineering, construction, and packaging in the United States, Western Europe, and Japan.
Despite its prevalence in the environment, no living organism is known to metabolize aluminium salts, but this aluminium is well tolerated by plants and animals. Because of the abundance of these salts, the potential for a biological role for them is of interest, and studies are ongoing. |
Aluminium | Physical characteristics | Physical characteristics |
Aluminium | Isotopes | Isotopes
Of aluminium isotopes, only is stable. This situation is common for elements with an odd atomic number. It is the only primordial aluminium isotope, i.e. the only one that has existed on Earth in its current form since the formation of the planet. It is therefore a mononuclidic element and its standard atomic weight is virtually the same as that of the isotope. This makes aluminium very useful in nuclear magnetic resonance (NMR), as its single stable isotope has a high NMR sensitivity. The standard atomic weight of aluminium is low in comparison with many other metals.
All other isotopes of aluminium are radioactive. The most stable of these is 26Al: while it was present along with stable 27Al in the interstellar medium from which the Solar System formed, having been produced by stellar nucleosynthesis as well, its half-life is only 717,000 years and therefore a detectable amount has not survived since the formation of the planet. However, minute traces of 26Al are produced from argon in the atmosphere by spallation caused by cosmic ray protons. The ratio of 26Al to 10Be has been used for radiodating of geological processes over 105 to 106 year time scales, in particular transport, deposition, sediment storage, burial times, and erosion. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.
The remaining isotopes of aluminium, with mass numbers ranging from 21 to 43, all have half-lives well under an hour. Three metastable states are known, all with half-lives under a minute. |
Aluminium | Electron shell | Electron shell
An aluminium atom has 13 electrons, arranged in an electron configuration of , with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminium are far lower than the fourth ionization energy alone. Such an electron configuration is shared with the other well-characterized members of its group, boron, gallium, indium, and thallium; it is also expected for nihonium. Aluminium can surrender its three outermost electrons in many chemical reactions (see below). The electronegativity of aluminium is 1.61 (Pauling scale).
alt=M. Tunes & S. Pogatscher, Montanuniversität Leoben 2019 No copyrights =)|left|thumb|upright=1.2|High-resolution STEM-HAADF micrograph of Al atoms viewed along the [001] zone axis.
A free aluminium atom has a radius of 143 pm. With the three outermost electrons removed, the radius shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At standard temperature and pressure, aluminium atoms (when not affected by atoms of other elements) form a face-centered cubic crystal system bound by metallic bonding provided by atoms' outermost electrons; hence aluminium (at these conditions) is a metal. This crystal system is shared by many other metals, such as lead and copper; the size of a unit cell of aluminium is comparable to that of those other metals. The system, however, is not shared by the other members of its group: boron has ionization energies too high to allow metallization, thallium has a hexagonal close-packed structure, and gallium and indium have unusual structures that are not close-packed like those of aluminium and thallium. The few electrons that are available for metallic bonding in aluminium are a probable cause for it being soft with a low melting point and low electrical resistivity. |
Aluminium | Bulk | Bulk
thumb|left|Aluminium ingot from furnace
Aluminium metal has an appearance ranging from silvery white to dull gray depending on its surface roughness. Aluminium mirrors provides high reflectivity for light in the ultraviolet, visible (on par with silver), and the far infrared region. Aluminium is also good at reflecting solar radiation, although prolonged exposure to sunlight in air can deteriorate the reflectivity of the metal; this may be prevented if aluminium is anodized, which adds a protective layer of oxide on the surface.
The density of aluminium is 2.70 g/cm3, about 1/3 that of steel, much lower than other commonly encountered metals, making aluminium parts easily identifiable through their lightness. Aluminium's low density compared to most other metals arises from the fact that its nuclei are much lighter, while difference in the unit cell size does not compensate for this difference. The only lighter metals are the metals of groups 1 and 2, which apart from beryllium and magnesium are too reactive for structural use (and beryllium is very toxic). Aluminium is not as strong or stiff as steel, but the low density makes up for this in the aerospace industry and for many other applications where light weight and relatively high strength are crucial.
Pure aluminium is quite soft and lacking in strength. In most applications various aluminium alloys are used instead because of their higher strength and hardness. The yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium is ductile, with a percent elongation of 50–70%, and malleable allowing it to be easily drawn and extruded. It is also easily machined and cast.
Aluminium is an excellent thermal and electrical conductor, having around 60% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of superconductivity, with a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of about 100 gauss (10 milliteslas). It is paramagnetic and thus essentially unaffected by static magnetic fields. The high electrical conductivity, however, means that it is strongly affected by alternating magnetic fields through the induction of eddy currents. |
Aluminium | Chemistry | Chemistry
Aluminium combines characteristics of pre- and post-transition metals. Since it has few available electrons for metallic bonding, like its heavier group 13 congeners, it has the characteristic physical properties of a post-transition metal, with longer-than-expected interatomic distances. Furthermore, as Al3+ is a small and highly charged cation, it is strongly polarizing and bonding in aluminium compounds tends towards covalency; this behavior is similar to that of beryllium (Be2+), and the two display an example of a diagonal relationship.
The underlying core under aluminium's valence shell is that of the preceding noble gas, whereas those of its heavier congeners gallium, indium, thallium, and nihonium also include a filled d-subshell and in some cases a filled f-subshell. Hence, the inner electrons of aluminium shield the valence electrons almost completely, unlike those of aluminium's heavier congeners. As such, aluminium is the most electropositive metal in its group, and its hydroxide is in fact more basic than that of gallium. Aluminium also bears minor similarities to the metalloid boron in the same group: AlX3 compounds are valence isoelectronic to BX3 compounds (they have the same valence electronic structure), and both behave as Lewis acids and readily form adducts. Additionally, one of the main motifs of boron chemistry is regular icosahedral structures, and aluminium forms an important part of many icosahedral quasicrystal alloys, including the Al–Zn–Mg class.
Aluminium has a high chemical affinity to oxygen, which renders it suitable for use as a reducing agent in the thermite reaction. A fine powder of aluminium reacts explosively on contact with liquid oxygen; under normal conditions, however, aluminium forms a thin oxide layer (~5 nm at room temperature) that protects the metal from further corrosion by oxygen, water, or dilute acid, a process termed passivation. Aluminium is not attacked by oxidizing acids because of its passivation. This allows aluminium to be used to store reagents such as nitric acid, concentrated sulfuric acid, and some organic acids.
In hot concentrated hydrochloric acid, aluminium reacts with water with evolution of hydrogen, and in aqueous sodium hydroxide or potassium hydroxide at room temperature to form aluminates—protective passivation under these conditions is negligible. Aqua regia also dissolves aluminium. Aluminium is corroded by dissolved chlorides, such as common sodium chloride. The oxide layer on aluminium is also destroyed by contact with mercury due to amalgamation or with salts of some electropositive metals. As such, the strongest aluminium alloys are less corrosion-resistant due to galvanic reactions with alloyed copper, and aluminium's corrosion resistance is greatly reduced by aqueous salts, particularly in the presence of dissimilar metals.
Aluminium reacts with most nonmetals upon heating, forming compounds such as aluminium nitride (AlN), aluminium sulfide (Al2S3), and the aluminium halides (AlX3). It also forms a wide range of intermetallic compounds involving metals from every group on the periodic table. |
Aluminium | Inorganic compounds | Inorganic compounds
The vast majority of compounds, including all aluminium-containing minerals and all commercially significant aluminium compounds, feature aluminium in the oxidation state 3+. The coordination number of such compounds varies, but generally Al3+ is either six- or four-coordinate. Almost all compounds of aluminium(III) are colorless.
thumb|upright=1.0|right|Aluminium hydrolysis as a function of pH. Coordinated water molecules are omitted.*
In aqueous solution, Al3+ exists as the hexaaqua cation [Al(H2O)6]3+, which has an approximate Ka of 10−5. Such solutions are acidic as this cation can act as a proton donor and progressively hydrolyze until a precipitate of aluminium hydroxide, Al(OH)3, forms. This is useful for clarification of water, as the precipitate nucleates on suspended particles in the water, hence removing them. Increasing the pH even further leads to the hydroxide dissolving again as aluminate, [Al(H2O)2(OH)4]−, is formed.
Aluminium hydroxide forms both salts and aluminates and dissolves in acid and alkali, as well as on fusion with acidic and basic oxides. This behavior of Al(OH)3 is termed amphoterism and is characteristic of weakly basic cations that form insoluble hydroxides and whose hydrated species can also donate their protons. One effect of this is that aluminium salts with weak acids are hydrolyzed in water to the aquated hydroxide and the corresponding nonmetal hydride: for example, aluminium sulfide yields hydrogen sulfide. However, some salts like aluminium carbonate exist in aqueous solution but are unstable as such; and only incomplete hydrolysis takes place for salts with strong acids, such as the halides, nitrate, and sulfate. For similar reasons, anhydrous aluminium salts cannot be made by heating their "hydrates": hydrated aluminium chloride is in fact not AlCl3·6H2O but [Al(H2O)6]Cl3, and the Al–O bonds are so strong that heating is not sufficient to break them and form Al–Cl bonds. This reaction is observed instead:
2[Al(H2O)6]Cl3 Al2O3 + 6 HCl + 9 H2O
All four trihalides are well known. Unlike the structures of the three heavier trihalides, aluminium fluoride (AlF3) features six-coordinate aluminium, which explains its involatility and insolubility as well as high heat of formation. Each aluminium atom is surrounded by six fluorine atoms in a distorted octahedral arrangement, with each fluorine atom being shared between the corners of two octahedra. Such {AlF6} units also exist in complex fluorides such as cryolite, Na3AlF6. AlF3 melts at and is made by reaction of aluminium oxide with hydrogen fluoride gas at .
With heavier halides, the coordination numbers are lower. The other trihalides are dimeric or polymeric with tetrahedral four-coordinate aluminium centers. Aluminium trichloride (AlCl3) has a layered polymeric structure below its melting point of but transforms on melting to Al2Cl6 dimers. At higher temperatures those increasingly dissociate into trigonal planar AlCl3 monomers similar to the structure of BCl3. Aluminium tribromide and aluminium triiodide form Al2X6 dimers in all three phases and hence do not show such significant changes of properties upon phase change. These materials are prepared by treating aluminium with the halogen. The aluminium trihalides form many addition compounds or complexes; their Lewis acidic nature makes them useful as catalysts for the Friedel–Crafts reactions. Aluminium trichloride has major industrial uses involving this reaction, such as in the manufacture of anthraquinones and styrene; it is also often used as the precursor for many other aluminium compounds and as a reagent for converting nonmetal fluorides into the corresponding chlorides (a transhalogenation reaction).
Aluminium forms one stable oxide with the chemical formula Al2O3, commonly called alumina. It can be found in nature in the mineral corundum, α-alumina; there is also a γ-alumina phase. Its crystalline form, corundum, is very hard (Mohs hardness 9), has a high melting point of , has very low volatility, is chemically inert, and a good electrical insulator, it is often used in abrasives (such as toothpaste), as a refractory material, and in ceramics, as well as being the starting material for the electrolytic production of aluminium. Sapphire and ruby are impure corundum contaminated with trace amounts of other metals. The two main oxide-hydroxides, AlO(OH), are boehmite and diaspore. There are three main trihydroxides: bayerite, gibbsite, and nordstrandite, which differ in their crystalline structure (polymorphs). Many other intermediate and related structures are also known. Most are produced from ores by a variety of wet processes using acid and base. Heating the hydroxides leads to formation of corundum. These materials are of central importance to the production of aluminium and are themselves extremely useful. Some mixed oxide phases are also very useful, such as spinel (MgAl2O4), Na-β-alumina (NaAl11O17), and tricalcium aluminate (Ca3Al2O6, an important mineral phase in Portland cement).
The only stable chalcogenides under normal conditions are aluminium sulfide (Al2S3), selenide (Al2Se3), and telluride (Al2Te3). All three are prepared by direct reaction of their elements at about and quickly hydrolyze completely in water to yield aluminium hydroxide and the respective hydrogen chalcogenide. As aluminium is a small atom relative to these chalcogens, these have four-coordinate tetrahedral aluminium with various polymorphs having structures related to wurtzite, with two-thirds of the possible metal sites occupied either in an orderly (α) or random (β) fashion; the sulfide also has a γ form related to γ-alumina, and an unusual high-temperature hexagonal form where half the aluminium atoms have tetrahedral four-coordination and the other half have trigonal bipyramidal five-coordination.
Four pnictides – aluminium nitride (AlN), aluminium phosphide (AlP), aluminium arsenide (AlAs), and aluminium antimonide (AlSb) – are known. They are all III-V semiconductors isoelectronic to silicon and germanium, all of which but AlN have the zinc blende structure. All four can be made by high-temperature (and possibly high-pressure) direct reaction of their component elements.
Aluminium alloys well with most other metals (with the exception of most alkali metals and group 13 metals) and over 150 intermetallics with other metals are known. Preparation involves heating fixed metals together in certain proportion, followed by gradual cooling and annealing. Bonding in them is predominantly metallic and the crystal structure primarily depends on efficiency of packing.
There are few compounds with lower oxidation states. A few aluminium(I) compounds exist: AlF, AlCl, AlBr, and AlI exist in the gaseous phase when the respective trihalide is heated with aluminium, and at cryogenic temperatures. A stable derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al4I4(NEt3)4. Al2O and Al2S also exist but are very unstable. Very simple aluminium(II) compounds are invoked or observed in the reactions of Al metal with oxidants. For example, aluminium monoxide, AlO, has been detected in the gas phase after explosion and in stellar absorption spectra. More thoroughly investigated are compounds of the formula R4Al2 which contain an Al–Al bond and where R is a large organic ligand. |
Aluminium | Organoaluminium compounds and related hydrides | Organoaluminium compounds and related hydrides
thumb|upright=1.0|Structure of trimethylaluminium, a compound that features five-coordinate carbon.
A variety of compounds of empirical formula AlR3 and AlR1.5Cl1.5 exist. The aluminium trialkyls and triaryls are reactive, volatile, and colorless liquids or low-melting solids. They catch fire spontaneously in air and react with water, thus necessitating precautions when handling them. They often form dimers, unlike their boron analogues, but this tendency diminishes for branched-chain alkyls (e.g. Pri, Bui, Me3CCH2); for example, triisobutylaluminium exists as an equilibrium mixture of the monomer and dimer. These dimers, such as trimethylaluminium (Al2Me6), usually feature tetrahedral Al centers formed by dimerization with some alkyl group bridging between both aluminium atoms. They are hard acids and react readily with ligands, forming adducts. In industry, they are mostly used in alkene insertion reactions, as discovered by Karl Ziegler, most importantly in "growth reactions" that form long-chain unbranched primary alkenes and alcohols, and in the low-pressure polymerization of ethene and propene. There are also some heterocyclic and cluster organoaluminium compounds involving Al–N bonds.
The industrially most important aluminium hydride is lithium aluminium hydride (LiAlH4), which is used as a reducing agent in organic chemistry. It can be produced from lithium hydride and aluminium trichloride. The simplest hydride, aluminium hydride or alane, is not as important. It is a polymer with the formula (AlH3)n, in contrast to the corresponding boron hydride that is a dimer with the formula (BH3)2. |
Aluminium | Natural occurrence | Natural occurrence |
Aluminium | Space | Space
Aluminium's per-particle abundance in the Solar System is 3.15 ppm (parts per million). It is the twelfth most abundant of all elements and third most abundant among the elements that have odd atomic numbers, after hydrogen and nitrogen. The only stable isotope of aluminium, 27Al, is the eighteenth most abundant nucleus in the universe. It is created almost entirely after fusion of carbon in massive stars that will later become Type II supernovas: this fusion creates 26Mg, which upon capturing free protons and neutrons, becomes aluminium. Some smaller quantities of 27Al are created in hydrogen burning shells of evolved stars, where 26Mg can capture free protons. Essentially all aluminium now in existence is 27Al. 26Al was present in the early Solar System with abundance of 0.005% relative to 27Al but its half-life of 728,000 years is too short for any original nuclei to survive; 26Al is therefore extinct. Unlike for 27Al, hydrogen burning is the primary source of 26Al, with the nuclide emerging after a nucleus of 25Mg catches a free proton. However, the trace quantities of 26Al that do exist are the most common gamma ray emitter in the interstellar gas; if the original 26Al were still present, gamma ray maps of the Milky Way would be brighter. |
Aluminium | Earth | Earth
thumb|Bauxite, a major aluminium ore. The red-brown color is due to the presence of iron oxide minerals.
Overall, the Earth is about 1.59% aluminium by mass (seventh in abundance by mass).William F McDonough The composition of the Earth. quake.mit.edu, archived by the Internet Archive Wayback Machine. Aluminium occurs in greater proportion in the Earth's crust than in the universe at large. This is because aluminium easily forms the oxide and becomes bound into rocks and stays in the Earth's crust, while less reactive metals sink to the core. In the Earth's crust, aluminium is the most abundant metallic element (8.23% by mass) and the third most abundant of all elements (after oxygen and silicon). A large number of silicates in the Earth's crust contain aluminium. In contrast, the Earth's mantle is only 2.38% aluminium by mass. Aluminium also occurs in seawater at a concentration of 0.41 μg/kg.
Because of its strong affinity for oxygen, aluminium is almost never found in the elemental state; instead it is found in oxides or silicates. Feldspars, the most common group of minerals in the Earth's crust, are aluminosilicates. Aluminium also occurs in the minerals beryl, cryolite, garnet, spinel, and turquoise. Impurities in Al2O3, such as chromium and iron, yield the gemstones ruby and sapphire, respectively. Native aluminium metal is extremely rare and can only be found as a minor phase in low oxygen fugacity environments, such as the interiors of certain volcanoes. Native aluminium has been reported in cold seeps in the northeastern continental slope of the South China Sea. It is possible that these deposits resulted from bacterial reduction of tetrahydroxoaluminate Al(OH)4−.
Although aluminium is a common and widespread element, not all aluminium minerals are economically viable sources of the metal. Almost all metallic aluminium is produced from the ore bauxite (AlOx(OH)3–2x). Bauxite occurs as a weathering product of low iron and silica bedrock in tropical climatic conditions. In 2017, most bauxite was mined in Australia, China, Guinea, and India. |
Aluminium | History | History
thumb|upright=0.75|Friedrich Wöhler, the chemist who first thoroughly described metallic elemental aluminium
The history of aluminium has been shaped by usage of alum. The first written record of alum, made by Greek historian Herodotus, dates back to the 5th century BCE. The ancients are known to have used alum as a dyeing mordant and for city defense. After the Crusades, alum, an indispensable good in the European fabric industry, was a subject of international commerce; it was imported to Europe from the eastern Mediterranean until the mid-15th century.
The nature of alum remained unknown. Around 1530, Swiss physician Paracelsus suggested alum was a salt of an earth of alum. In 1595, German doctor and chemist Andreas Libavius experimentally confirmed this. In 1722, German chemist Friedrich Hoffmann announced his belief that the base of alum was a distinct earth. In 1754, German chemist Andreas Sigismund Marggraf synthesized alumina by boiling clay in sulfuric acid and subsequently adding potash.
Attempts to produce aluminium date back to 1760. The first successful attempt, however, was completed in 1824 by Danish physicist and chemist Hans Christian Ørsted. He reacted anhydrous aluminium chloride with potassium amalgam, yielding a lump of metal looking similar to tin. He presented his results and demonstrated a sample of the new metal in 1825. In 1827, German chemist Friedrich Wöhler repeated Ørsted's experiments but did not identify any aluminium. (The reason for this inconsistency was only discovered in 1921.) He conducted a similar experiment in the same year by mixing anhydrous aluminium chloride with potassium (the Wöhler process) and produced a powder of aluminium. In 1845, he was able to produce small pieces of the metal and described some physical properties of this metal. For many years thereafter, Wöhler was credited as the discoverer of aluminium.
thumb|upright=0.75|right|The statue of Anteros in Piccadilly Circus, London, was made in 1893 and is one of the first statues cast in aluminium.
As Wöhler's method could not yield great quantities of aluminium, the metal remained rare; its cost exceeded that of gold. The first industrial production of aluminium was established in 1856 by French chemist Henri Etienne Sainte-Claire Deville and companions. Deville had discovered that aluminium trichloride could be reduced by sodium, which was more convenient and less expensive than potassium, which Wöhler had used. Even then, aluminium was still not of great purity and produced aluminium differed in properties by sample. Because of its electricity-conducting capacity, aluminium was used as the cap of the Washington Monument, completed in 1885, the tallest building in the world at the time. The non-corroding metal cap was intended to serve as a lightning rod peak.
The first industrial large-scale production method was independently developed in 1886 by French engineer Paul Héroult and American engineer Charles Martin Hall; it is now known as the Hall–Héroult process. The Hall–Héroult process converts alumina into metal. Austrian chemist Carl Joseph Bayer discovered a way of purifying bauxite to yield alumina, now known as the Bayer process, in 1889. Modern production of aluminium is based on the Bayer and Hall–Héroult processes.
As large-scale production caused aluminium prices to drop, the metal became widely used in jewelry, eyeglass frames, optical instruments, tableware, and foil, and other everyday items in the 1890s and early 20th century. Aluminium's ability to form hard yet light alloys with other metals provided the metal with many uses at the time. During World War I, major governments demanded large shipments of aluminium for light strong airframes; during World War II, demand by major governments for aviation was even higher.
From the early 20th century to 1980, the aluminium industry was characterized by cartelization, as aluminium firms colluded to keep prices high and stable. The first aluminium cartel, the Aluminium Association, was founded in 1901 by the Pittsburgh Reduction Company (renamed Alcoa in 1907) and Aluminium Industrie AG. The British Aluminium Company, Produits Chimiques d’Alais et de la Camargue, and Société Electro-Métallurgique de Froges also joined the cartel.
By the mid-20th century, aluminium had become a part of everyday life and an essential component of housewares. In 1954, production of aluminium surpassed that of copper, historically second in production only to iron, making it the most produced non-ferrous metal. During the mid-20th century, aluminium emerged as a civil engineering material, with building applications in both basic construction and interior finish work, and increasingly being used in military engineering, for both airplanes and land armor vehicle engines. Earth's first artificial satellite, launched in 1957, consisted of two separate aluminium semi-spheres joined and all subsequent space vehicles have used aluminium to some extent. The aluminium can was invented in 1956 and employed as a storage for drinks in 1958.
thumb|upright=1.0|lang=en|World production of aluminium since 1900
Throughout the 20th century, the production of aluminium rose rapidly: while the world production of aluminium in 1900 was 6,800 metric tons, the annual production first exceeded 100,000 metric tons in 1916; 1,000,000 tons in 1941; 10,000,000 tons in 1971. In the 1970s, the increased demand for aluminium made it an exchange commodity; it entered the London Metal Exchange, the oldest industrial metal exchange in the world, in 1978. The output continued to grow: the annual production of aluminium exceeded 50,000,000 metric tons in 2013.
The real price for aluminium declined from $14,000 per metric ton in 1900 to $2,340 in 1948 (in 1998 United States dollars). Extraction and processing costs were lowered over technological progress and the scale of the economies. However, the need to exploit lower-grade poorer quality deposits and the use of fast increasing input costs (above all, energy) increased the net cost of aluminium; the real price began to grow in the 1970s with the rise of energy cost. Production moved from the industrialized countries to countries where production was cheaper. Production costs in the late 20th century changed because of advances in technology, lower energy prices, exchange rates of the United States dollar, and alumina prices. The BRIC countries' combined share in primary production and primary consumption grew substantially in the first decade of the 21st century. China is accumulating an especially large share of the world's production thanks to an abundance of resources, cheap energy, and governmental stimuli; it also increased its consumption share from 2% in 1972 to 40% in 2010. In the United States, Western Europe, and Japan, most aluminium was consumed in transportation, engineering, construction, and packaging. In 2021, prices for industrial metals such as aluminium have soared to near-record levels as energy shortages in China drive up costs for electricity. |
Aluminium | Etymology | Etymology
The names aluminium and aluminum are derived from the word alumine, an obsolete term for alumina, the primary naturally occurring oxide of aluminium. Alumine was borrowed from French, which in turn derived it from alumen, the classical Latin name for alum, the mineral from which it was collected. The Latin word alumen stems from the Proto-Indo-European root *alu- meaning "bitter" or "beer".
thumb|upright|1897 American advertisement featuring the aluminum spelling |
Aluminium | Origins | Origins
British chemist Humphry Davy, who performed a number of experiments aimed to isolate the metal, is credited as the person who named the element. The first name proposed for the metal to be isolated from alum was alumium, which Davy suggested in an 1808 article on his electrochemical research, published in Philosophical Transactions of the Royal Society. It appeared that the name was created from the English word alum and the Latin suffix -ium; but it was customary then to give elements names originating in Latin, so this name was not adopted universally. This name was criticized by contemporary chemists from France, Germany, and Sweden, who insisted the metal should be named for the oxide, alumina, from which it would be isolated. The English name alum does not come directly from Latin, whereas alumine/alumina comes from the Latin word alumen (upon declension, alumen changes to alumin-).
One example was Essai sur la Nomenclature chimique (July 1811), written in French by a Swedish chemist, Jöns Jacob Berzelius, in which the name aluminium is given to the element that would be synthesized from alum.. (Another article in the same journal issue also refers to the metal whose oxide is the basis of sapphire, i.e. the same metal, as to aluminium.). A January 1811 summary of one of Davy's lectures at the Royal Society mentioned the name aluminium as a possibility. The next year, Davy published a chemistry textbook in which he used the spelling aluminum. Both spellings have coexisted since. Their usage is currently regional: aluminum dominates in the United States and Canada; aluminium is prevalent in the rest of the English-speaking world. |
Aluminium | Spelling | Spelling
In 1812, British scientist Thomas Young wrote an anonymous review of Davy's book, in which he proposed the name aluminium instead of aluminum, which he thought had a "less classical sound". This name persisted: although the spelling was occasionally used in Britain, the American scientific language used from the start.
Ludwig Wilhelm Gilbert had proposed Thonerde-metall, after the German "Thonerde" for alumina, in his Annalen der Physik but that name never caught on at all even in Germany. Joseph W. Richards in 1891 found just one occurrence of argillium in Swedish, from the French "argille" for clay. The French themselves had used aluminium from the start. However, in England and Germany Davy's spelling aluminum was initially used; until German chemist Friedrich Wöhler published his account of the Wöhler process in 1827 in which he used the spelling aluminium, which caused that spelling's largely wholesale adoption in England and Germany, with the exception of a small number of what Richards characterized as "patriotic" English chemists that were "averse to foreign innovations" who occasionally still used aluminum.
Most scientists throughout the world used in the 19th century; and it was entrenched in several other European languages, such as French, German, and Dutch.
In 1828, an American lexicographer, Noah Webster, entered only the aluminum spelling in his American Dictionary of the English Language. In the 1830s, the spelling gained usage in the United States; by the 1860s, it had become the more common spelling there outside science. In 1892, Hall used the spelling in his advertising handbill for his new electrolytic method of producing the metal, despite his constant use of the spelling in all the patents he filed between 1886 and 1903. It is unknown whether this spelling was introduced by mistake or intentionally, but Hall preferred aluminum since its introduction because it resembled platinum, the name of a prestigious metal. By 1890, both spellings had been common in the United States, the spelling being slightly more common; by 1895, the situation had reversed; by 1900, aluminum had become twice as common as aluminium; in the next decade, the spelling dominated American usage. In 1925, the American Chemical Society adopted this spelling.
The International Union of Pure and Applied Chemistry (IUPAC) adopted aluminium as the standard international name for the element in 1990. In 1993, they recognized aluminum as an acceptable variant; the most recent 2005 edition of the IUPAC nomenclature of inorganic chemistry also acknowledges this spelling. IUPAC official publications use the spelling as primary, and they list both where it is appropriate. |
Aluminium | Production and refinement | Production and refinement
+World's largest producing countries of aluminium, 2024 Country Output(thousand tons) 43,000 4,200 3,800 3,300 2,700 1,600 1,500 1,300 1,100 870 780 670 Other countries 6,800 Total 72,000
The production of aluminium starts with the extraction of bauxite rock from the ground. The bauxite is processed and transformed using the Bayer process into alumina, which is then processed using the Hall–Héroult process, resulting in the final aluminium.
Aluminium production is highly energy-consuming, and so the producers tend to locate smelters in places where electric power is both plentiful and inexpensive. Production of one kilogram of aluminium requires 7 kilograms of oil energy equivalent, as compared to 1.5 kilograms for steel and 2 kilograms for plastic. As of 2024, the world's largest producers of aluminium were China, Russia, India, Canada, and the United Arab Emirates, while China is by far the top producer of aluminium with a world share of over 55%.
According to the International Resource Panel's Metal Stocks in Society report, the global per capita stock of aluminium in use in society (i.e. in cars, buildings, electronics, etc.) is . Much of this is in more-developed countries ( per capita) rather than less-developed countries ( per capita). |
Aluminium | Bayer process | Bayer process
Bauxite is converted to alumina by the Bayer process. Bauxite is blended for uniform composition and then is ground fine. The resulting slurry is mixed with a hot solution of sodium hydroxide; the mixture is then treated in a digester vessel at a pressure well above atmospheric, dissolving the aluminium hydroxide in bauxite while converting impurities into relatively insoluble compounds:
After this reaction, the slurry is at a temperature above its atmospheric boiling point. It is cooled by removing steam as pressure is reduced. The bauxite residue is separated from the solution and discarded. The solution, free of solids, is seeded with small crystals of aluminium hydroxide; this causes decomposition of the [Al(OH)4]− ions to aluminium hydroxide. After about half of aluminium has precipitated, the mixture is sent to classifiers. Small crystals of aluminium hydroxide are collected to serve as seeding agents; coarse particles are converted to alumina by heating; the excess solution is removed by evaporation, (if needed) purified, and recycled. |
Aluminium | Hall–Héroult process | Hall–Héroult process
thumb|upright=0.75|right|Extrusion billets of aluminium
The conversion of alumina to aluminium is achieved by the Hall–Héroult process. In this energy-intensive process, a solution of alumina in a molten () mixture of cryolite (Na3AlF6) with calcium fluoride is electrolyzed to produce metallic aluminium. The liquid aluminium sinks to the bottom of the solution and is tapped off, and usually cast into large blocks called aluminium billets for further processing.
Anodes of the electrolysis cell are made of carbon—the most resistant material against fluoride corrosion—and either bake at the process or are prebaked. The former, also called Söderberg anodes, are less power-efficient and fumes released during baking are costly to collect, which is why they are being replaced by prebaked anodes even though they save the power, energy, and labor to prebake the cathodes. Carbon for anodes should be preferably pure so that neither aluminium nor the electrolyte is contaminated with ash. Despite carbon's resistivity against corrosion, it is still consumed at a rate of 0.4–0.5 kg per each kilogram of produced aluminium. Cathodes are made of anthracite; high purity for them is not required because impurities leach only very slowly. The cathode is consumed at a rate of 0.02–0.04 kg per each kilogram of produced aluminium. A cell is usually terminated after 2–6 years following a failure of the cathode.
The Hall–Heroult process produces aluminium with a purity of above 99%. Further purification can be done by the Hoopes process. This process involves the electrolysis of molten aluminium with a sodium, barium, and aluminium fluoride electrolyte. The resulting aluminium has a purity of 99.99%.
Electric power represents about 20 to 40% of the cost of producing aluminium, depending on the location of the smelter. Aluminium production consumes roughly 5% of electricity generated in the United States. Because of this, alternatives to the Hall–Héroult process have been researched, but none has turned out to be economically feasible. |
Aluminium | Recycling | Recycling
thumb|Common bins for recyclable waste along with a bin for unrecyclable waste. The bin with a yellow top is labeled "aluminum". Rhodes, Greece.
Recovery of the metal through recycling has become an important task of the aluminium industry. Recycling was a low-profile activity until the late 1960s, when the growing use of aluminium beverage cans brought it to public awareness. Recycling involves melting the scrap, a process that requires only 5% of the energy used to produce aluminium from ore, though a significant part (up to 15% of the input material) is lost as dross (ash-like oxide). An aluminium stack melter produces significantly less dross, with values reported below 1%.
White dross from primary aluminium production and from secondary recycling operations still contains useful quantities of aluminium that can be extracted industrially. The process produces aluminium billets, together with a highly complex waste material. This waste is difficult to manage. It reacts with water, releasing a mixture of gases including, among others, acetylene, hydrogen sulfide and significant amounts of ammonia. Despite these difficulties, the waste is used as a filler in asphalt and concrete. Its potential for hydrogen production has also been considered and researched. |
Aluminium | Applications | Applications
thumb|upright=1.0|right|Aluminium-bodied Austin A40 Sports (c. 1951) |
Aluminium | Metal | Metal
The global production of aluminium in 2016 was 58.8 million metric tons. It exceeded that of any other metal except iron (1,231 million metric tons).
Aluminium is almost always alloyed, which markedly improves its mechanical properties, especially when tempered. For example, the common aluminium foils and beverage cans are alloys of 92% to 99% aluminium. The main alloying agents for both wrought and cast aluminium are copper, zinc, magnesium, manganese, and silicon (e.g., duralumin) with the levels of other metals in a few percent by weight.
thumb|upright=1.0|Aluminium can
The major uses for aluminium are in:
Transportation (automobiles, aircraft, trucks, railway cars, marine vessels, bicycles, spacecraft, etc.). Aluminium is used because of its low density;
Packaging (cans, foil, frame, etc.). Aluminium is used because it is non-toxic (see below), non-adsorptive, and splinter-proof;
Building and construction (windows, doors, siding, building wire, sheathing, roofing, etc.). Since steel is cheaper, aluminium is used when lightness, corrosion resistance, or engineering features are important;
Electricity-related uses (conductor alloys, motors, and generators, transformers, capacitors, etc.). Aluminium is used because it is relatively cheap, highly conductive, has adequate mechanical strength and low density, and resists corrosion;
A wide range of household items, from cooking utensils to furniture. Low density, good appearance, ease of fabrication, and durability are the key factors of aluminium usage;
Machinery and equipment (processing equipment, pipes, tools). Aluminium is used because of its corrosion resistance, non-pyrophoricity, and mechanical strength. |
Aluminium | Compounds | Compounds
The great majority (about 90%) of aluminium oxide is converted to metallic aluminium. Being a very hard material (Mohs hardness 9), alumina is widely used as an abrasive; being extraordinarily chemically inert, it is useful in highly reactive environments such as high pressure sodium lamps. Aluminium oxide is commonly used as a catalyst for industrial processes; e.g. the Claus process to convert hydrogen sulfide to sulfur in refineries and to alkylate amines. Many industrial catalysts are supported by alumina, meaning that the expensive catalyst material is dispersed over a surface of the inert alumina. Another principal use is as a drying agent or absorbent.
thumb|upright|Laser deposition of alumina on a substrate
Several sulfates of aluminium have industrial and commercial application. Aluminium sulfate (in its hydrate form) is produced on the annual scale of several millions of metric tons. About two-thirds is consumed in water treatment. The next major application is in the manufacture of paper. It is also used as a mordant in dyeing, in pickling seeds, deodorizing of mineral oils, in leather tanning, and in production of other aluminium compounds. Two kinds of alum, ammonium alum and potassium alum, were formerly used as mordants and in leather tanning, but their use has significantly declined following availability of high-purity aluminium sulfate. Anhydrous aluminium chloride is used as a catalyst in chemical and petrochemical industries, the dyeing industry, and in synthesis of various inorganic and organic compounds. Aluminium hydroxychlorides are used in purifying water, in the paper industry, and as antiperspirants. Sodium aluminate is used in treating water and as an accelerator of solidification of cement.
Many aluminium compounds have niche applications, for example:
Aluminium acetate in solution is used as an astringent.
Aluminium phosphate is used in the manufacture of glass, ceramic, pulp and paper products, cosmetics, paints, varnishes, and in dental cement.
Aluminium hydroxide is used as an antacid, and mordant; it is used also in water purification, the manufacture of glass and ceramics, and in the waterproofing of fabrics.
Lithium aluminium hydride is a powerful reducing agent used in organic chemistry.
Organoaluminiums are used as Lewis acids and co-catalysts.
Methylaluminoxane is a co-catalyst for Ziegler–Natta olefin polymerization to produce vinyl polymers such as polyethene.
Aqueous aluminium ions (such as aqueous aluminium sulfate) are used to treat against fish parasites such as Gyrodactylus salaris.
In many vaccines, certain aluminium salts serve as an immune adjuvant (immune response booster) to allow the protein in the vaccine to achieve sufficient potency as an immune stimulant. Until 2004, most of the adjuvants used in vaccines were aluminium-adjuvanted. |
Aluminium | Biology | Biology
thumb|upright=1.3|Schematic of aluminium absorption by human skin.
Despite its widespread occurrence in the Earth's crust, aluminium has no known function in biology. At pH 6–9 (relevant for most natural waters), aluminium precipitates out of water as the hydroxide and is hence not available; most elements behaving this way have no biological role or are toxic. Aluminium sulfate has an LD50 of 6207 mg/kg (oral, mouse), which corresponds to 435 grams (about one pound) for a mouse. |
Aluminium | Toxicity | Toxicity
Aluminium is classified as a non-carcinogen by the United States Department of Health and Human Services. A review published in 1988 said that there was little evidence that normal exposure to aluminium presents a risk to healthy adult, and a 2014 multi-element toxicology review was unable to find deleterious effects of aluminium consumed in amounts not greater than 40 mg/day per kg of body mass. Most aluminium consumed will leave the body in feces; most of the small part of it that enters the bloodstream, will be excreted via urine; nevertheless some aluminium does pass the blood-brain barrier and is lodged preferentially in the brains of Alzheimer's patients. Evidence published in 1989 indicates that, for Alzheimer's patients, aluminium may act by electrostatically crosslinking proteins, thus down-regulating genes in the superior temporal gyrus. |
Aluminium | Effects | Effects
Aluminium, although rarely, can cause vitamin D-resistant osteomalacia, erythropoietin-resistant microcytic anemia, and central nervous system alterations. People with kidney insufficiency are especially at a risk. Chronic ingestion of hydrated aluminium silicates (for excess gastric acidity control) may result in aluminium binding to intestinal contents and increased elimination of other metals, such as iron or zinc; sufficiently high doses (>50 g/day) can cause anemia.
thumb|upright=1.3|There are five major aluminium forms absorbed by human body: the free solvated trivalent cation (Al3+(aq)); low-molecular-weight, neutral, soluble complexes (LMW-Al0(aq)); high-molecular-weight, neutral, soluble complexes (HMW-Al0(aq)); low-molecular-weight, charged, soluble complexes (LMW-Al(L)n+/−(aq)); nano and micro-particulates (Al(L)n(s)). They are transported across cell membranes or cell epi-/endothelia through five major routes: (1) paracellular; (2) transcellular; (3) active transport; (4) channels; (5) adsorptive or receptor-mediated endocytosis.
During the 1988 Camelford water pollution incident, people in Camelford had their drinking water contaminated with aluminium sulfate for several weeks. A final report into the incident in 2013 concluded it was unlikely that this had caused long-term health problems.
Aluminium has been suspected of being a possible cause of Alzheimer's disease, but research into this for over 40 years has found, , no good evidence of causal effect.
Aluminium increases estrogen-related gene expression in human breast cancer cells cultured in the laboratory. In very high doses, aluminium is associated with altered function of the blood–brain barrier. A small percentage of people have contact allergies to aluminium and experience itchy red rashes, headache, muscle pain, joint pain, poor memory, insomnia, depression, asthma, irritable bowel syndrome, or other symptoms upon contact with products containing aluminium.
Exposure to powdered aluminium or aluminium welding fumes can cause pulmonary fibrosis. Fine aluminium powder can ignite or explode, posing another workplace hazard. |
Aluminium | Exposure routes | Exposure routes
Food is the main source of aluminium. Drinking water contains more aluminium than solid food; however, aluminium in food may be absorbed more than aluminium from water. Major sources of human oral exposure to aluminium include food (due to its use in food additives, food and beverage packaging, and cooking utensils), drinking water (due to its use in municipal water treatment), and aluminium-containing medications (particularly antacid/antiulcer and buffered aspirin formulations). Dietary exposure in Europeans averages to 0.2–1.5 mg/kg/week but can be as high as 2.3 mg/kg/week. Higher exposure levels of aluminium are mostly limited to miners, aluminium production workers, and dialysis patients.
Consumption of antacids, antiperspirants, vaccines, and cosmetics provide possible routes of exposure. Consumption of acidic foods or liquids with aluminium enhances aluminium absorption, and maltol has been shown to increase the accumulation of aluminium in nerve and bone tissues. |
Aluminium | Treatment | Treatment
In case of suspected sudden intake of a large amount of aluminium, the only treatment is deferoxamine mesylate which may be given to help eliminate aluminium from the body by chelation therapy.Aluminum Toxicity from NYU Langone Medical Center. Last reviewed November 2012 by Igor Puzanov, MD However, this should be applied with caution as this reduces not only aluminium body levels, but also those of other metals such as copper or iron. |
Aluminium | Environmental effects | Environmental effects
thumb|upright=1.0|"Bauxite tailings" storage facility in Stade, Germany. The aluminium industry generates about 70 million tons of this waste annually.
High levels of aluminium occur near mining sites; small amounts of aluminium are released to the environment at coal-fired power plants or incinerators. Aluminium in the air is washed out by the rain or normally settles down but small particles of aluminium remain in the air for a long time.
Acidic precipitation is the main natural factor to mobilize aluminium from natural sources and the main reason for the environmental effects of aluminium; however, the main factor of presence of aluminium in salt and freshwater are the industrial processes that also release aluminium into air.
In water, aluminium acts as a toxiс agent on gill-breathing animals such as fish when the water is acidic, in which aluminium may precipitate on gills, which causes loss of plasma- and hemolymph ions leading to osmoregulatory failure. Organic complexes of aluminium may be easily absorbed and interfere with metabolism in mammals and birds, even though this rarely happens in practice.
Aluminium is primary among the factors that reduce plant growth on acidic soils. Although it is generally harmless to plant growth in pH-neutral soils, in acid soils the concentration of toxic Al3+ cations increases and disturbs root growth and function. Wheat has developed a tolerance to aluminium, releasing organic compounds that bind to harmful aluminium cations. Sorghum is believed to have the same tolerance mechanism.
Aluminium production possesses its own challenges to the environment on each step of the production process. The major challenge is the emission of greenhouse gases. These gases result from electrical consumption of the smelters and the byproducts of processing. The most potent of these gases are perfluorocarbons, namely CF4 and C2F6, from the smelting process.
Biodegradation of metallic aluminium is extremely rare; most aluminium-corroding organisms do not directly attack or consume the aluminium, but instead produce corrosive wastes. See also the abstract of . The fungus Geotrichum candidum can consume the aluminium in compact discs. The bacterium Pseudomonas aeruginosa and the fungus Cladosporium resinae are commonly detected in aircraft fuel tanks that use kerosene-based fuels (not avgas), and laboratory cultures can degrade aluminium. |
Aluminium | See also | See also
Aluminium granules
Aluminium joining
Aluminium–air battery
Aluminized steel, for corrosion resistance and other properties
Aluminized screen, for display devices
Aluminized cloth, to reflect heat
Aluminized mylar, to reflect heat
Panel edge staining
Quantum clock |
Aluminium | Notes | Notes |
Aluminium | References | References |
Aluminium | Bibliography | Bibliography
|
Aluminium | Further reading | Further reading
Mimi Sheller, Aluminum Dream: The Making of Light Modernity. Cambridge, Mass.: Massachusetts Institute of Technology Press, 2014. |
Aluminium | External links | External links
Aluminium at The Periodic Table of Videos (University of Nottingham)
Toxicological Profile for Aluminum (PDF) (September 2008) – 357-page report from the United States Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry
Aluminum entry (last reviewed 30 October 2019) in the NIOSH Pocket Guide to Chemical Hazards published by the CDC's National Institute for Occupational Safety and Health
Current and historical prices (1998–present) for aluminum futures on the global commodities market
Category:Chemical elements
Category:Post-transition metals
Aluminium
Category:Electrical conductors
Category:Pyrotechnic fuels
Category:Airship technology
Category:Reducing agents
Category:E-number additives
Category:Native element minerals
Category:Chemical elements with face-centered cubic structure |
Aluminium | Table of Content | other uses, Physical characteristics, Isotopes, Electron shell, Bulk, Chemistry, Inorganic compounds, Organoaluminium compounds and related hydrides, Natural occurrence, Space, Earth, History, Etymology, Origins, Spelling, Production and refinement, Bayer process, Hall–Héroult process, Recycling, Applications, Metal, Compounds, Biology, Toxicity, Effects, Exposure routes, Treatment, Environmental effects, See also, Notes, References, Bibliography, Further reading, External links |
Advanced Chemistry | Short description | Advanced Chemistry is a German hip hop group from Heidelberg in Baden-Württemberg, South Germany. Advanced Chemistry was founded in 1987 by Toni L, Linguist, Gee-One, DJ Mike MD (Mike Dippon) and MC Torch. Each member of the group holds German citizenship, and Toni L, Linguist, and Torch are of Italian, Ghanaian, and Haitian backgrounds, respectively.Pennay, Mark "Rap in Germany" in Mitchell, Tony ed. Global Noise. Middletown: Wesleyan University Press, 2001.
Influenced by North American socially conscious rap and the Native tongues movement, Advanced Chemistry is regarded as one of the main pioneers in German hip hop. They were one of the first groups to rap in German (although their name is in English). Furthermore, their songs tackled controversial social and political issues, distinguishing them from early German hip hop group "Die Fantastischen Vier" (The Fantastic Four), which had a more light-hearted, playful, party image. |
Advanced Chemistry | Career | Career
Advanced Chemistry frequently rapped about their lives and experiences as children of immigrants, exposing the marginalization experienced by most ethnic minorities in Germany, and the feelings of frustration and resentment that being denied a German identity can cause.Bennett, Andy. "Hip-Hop am Main, Rappin' on the Tyne: Hip-hop Culture as a Local Construct in Two European Cities." In That's the Joint!: The Hip-hop Studies Reader, 177-200. New York; London: Routledge, 2004, p. 183-184 The song "Fremd im eigenen Land" (Foreign in your own nation) was released by Advanced Chemistry in November 1992. The single became a staple in the German hip hop scene. It made a strong statement about the status of immigrants throughout Germany, as the group was composed of multi-national and multi-racial members. The video shows several members brandishing their German passports as a demonstration of their German citizenship to skeptical and unaccepting 'ethnic' Germans.
This idea of national identity is important, as many rap artists in Germany have been of foreign origin. These so-called Gastarbeiter (guest workers) children saw breakdance, graffiti, rap music, and hip hop culture as a means of expressing themselves.Schmidt, Johannes. Die Unterrichtspraxis/Teaching German>Vol. 36, No. 1. (Spring, 2003) pp. 1-14. Since the release of "Fremd im eigenen Land", many other German-language rappers have also tried to confront anti-immigrant ideas and develop themes of citizenship. However, though many ethnic minority youth in Germany find these German identity themes appealing, others view the desire of immigrants to be seen as German negatively, and they have actively sought to revive and recreate concepts of identity in connection to traditional ethnic origins.
Advanced Chemistry helped to found the German chapter of the Zulu nation.http://leaveyournineathome.wordpress.com/2007/10/13/german-hip-hop-1-advanced-chemistry/. Accessed March 26. Last updated October 13, 2007.
The rivalry between Advanced Chemistry and Die Fantastischen Vier has served to highlight a dichotomy in the routes that hip hop has taken in becoming a part of the German soundscape. While Die Fantastischen Vier may be said to view hip hop primarily as an aesthetic art form, Advanced Chemistry understand hip hop as being inextricably linked to the social and political circumstances under which it is created. For Advanced Chemistry, hip hop is a “vehicle of general human emancipation”.Brown, Timothy S. "'Keeping it Real' in a Different 'Hood:(African-) Americanization and Hip-hop in Germany." In The Vinyl Ain'tFinal: Hip Hop and the Globalization of Black Popular Culture, ed. by Dipannita Basu and Sidney J. Lemelle, 137-50. London In their undertaking of social and political issues, the band introduced the term "Afro-German" into the context of German hip hop, and the theme of race is highlighted in much of their music.
With the release of the single “Fremd im eigenen Land”, Advanced Chemistry separated itself from the rest of the rap being produced in Germany. This single was the first of its kind to go beyond simply imitating US rap and addressed the current issues of the time. Fremd im eigenen Land which translates to “foreign in my own country” dealt with the widespread racism that non-white German citizens faced. This change from simple imitation to political commentary was the start of German identification with rap. The sound of “Fremd im eigenen Land” was influenced by the 'wall of noise' created by Public Enemy's producers, The Bomb Squad.The Bomb Squad
After the reunification of Germany, an abundance of anti-immigrant sentiment emerged, as well as attacks on the homes of refugees in the early 1990s. Advanced Chemistry came to prominence in the wake of these actions because of their pro-multicultural society stance in their music. Advanced Chemistry's attitudes revolve around their attempts to create a distinct "Germanness" in hip hop, as opposed to imitating American hip hop as other groups had done. Torch has said, "What the Americans do is exotic for us because we don't live like they do. What they do seems to be more interesting and newer. But not for me. For me it's more exciting to experience my fellow Germans in new contexts...For me, it's interesting to see what the kids try to do that's different from what I know."Brown, Timothy S. “‘Keeping it Real’ in a Different ‘Hood: (African-) Americanization and Hip-hop in Germany.” In The Vinyl Ain’t Final: Hip Hop and the Globalization of Black Popular Culture, ed. by Dipannita Basu and Sidney J. Lemelle, 137-50. London; A Advanced Chemistry were the first to use the term "Afro-German" in a hip hop context. This was part of the pro-immigrant political message they sent via their music.
While Advanced Chemistry's use of the German language in their rap allows them to make claims to authenticity and true German heritage, bolstering pro-immigration sentiment, their style can also be problematic for immigrant notions of any real ethnic roots. Indeed, part of the Turkish ethnic minority of Frankfurt views Advanced Chemistry's appeal to the German image as a "symbolic betrayal of the right of ethnic minorities to 'roots' or to any expression of cultural heritage." In this sense, their rap represents a complex social discourse internal to the German soundscape in which they attempt to negotiate immigrant assimilation into a xenophobic German culture with the maintenance of their own separate cultural traditions. It is quite possibly the feelings of alienation from the pure-blooded German demographic that drive Advanced Chemistry to attack nationalistic ideologies by asserting their "Germanness" as a group composed primarily of ethnic others. The response to this pseudo-German authenticity can be seen in what Andy Bennett refers to as "alternative forms of local hip hop culture which actively seek to rediscover and, in many cases, reconstruct notions of identity tied to cultural roots."Bennett, Andy. "Hip-Hop am Main, Rappin' on the Tyne: Hip-hop Culture as a Local Construct in Two European Cities." In That's the Joint!: The Hip-hop Studies Reader, 177-200. New York; London: Routledge, 2004. These alternative local hip hop cultures include oriental hip hop, the members of which cling to their Turkish heritage and are confused by Advanced Chemistry's elicitation of a German identity politics to which they technically do not belong. This cultural binary illustrates that rap has taken different routes in Germany and that, even among an already isolated immigrant population, there is still disunity and, especially, disagreement on the relative importance of assimilation versus cultural defiance. According to German hip hop enthusiast 9@home, Advanced Chemistry is part of a "hip-hop movement [which] took a clear stance for the minorities and against the [marginalization] of immigrants who...might be German on paper, but not in real life,"9@home. "German Hip Hop 1: Advanced Chemistry." Leave Your Nine at Home. 13 Oct. 2007. Vanila Mist. 27 Mar. 2008 which speaks to the group's hope of actually being recognized as German citizens and not foreigners, despite their various other ethnic and cultural ties. |
Advanced Chemistry | Influences | Influences
Advanced Chemistry's work was rooted in German history and the country's specific political realities. However, they also drew inspiration from African-American hip-hop acts like A Tribe Called Quest and Public Enemy, who had helped bring a soulful sound and political consciousness to American hip-hop. One member, Torch, later explicitly listed his references on his solo song "Als (When I Was in School):" "My favorite subject, which was quickly discovered poetry in load Poets, awakens the intellect or policy at Chuck D I'll never forget the lyrics by Public Enemy." Torch goes on to list other American rappers like Biz Markie, Big Daddy Kane and Dr. Dre as influences. |
Advanced Chemistry | Discography | Discography
1992 - "Fremd im eigenen Land" (12"/MCD, MZEE)
1993 - "Welcher Pfad führt zur Geschichte" (12"/MCD, MZEE)
1994 - "Operation § 3" (12"/MCD)
1994 - "Dir fehlt der Funk!" (12"/MCD)
1995 - Advanced Chemistry (2xLP/CD) |
Advanced Chemistry | External links | External links
Official Website of MC Torch
Website of Toni L
Official Website of Linguist
Official Website DJ Mike MD (Mike Dippon)
Website of 360° Records |
Advanced Chemistry | Bibliography | Bibliography
El-Tayeb, Fatima “‘If You Cannot Pronounce My Name, You Can Just Call Me
Pride.’ Afro-German Activism, Gender, and Hip Hop,” Gender & History15/3(2003):459-485.
Felbert, Oliver von. “Die Unbestechlichen.” Spex (March 1993): 50–53.
Weheliye, Alexander G. Phonographies:Grooves in Sonic Afro-Modernity, Duke University Press, 2005. |
Advanced Chemistry | References | References
Category:German hip-hop groups |
Advanced Chemistry | Table of Content | Short description, Career, Influences, Discography, External links, Bibliography, References |
Anglican Communion | short description | The Anglican Communion is a Christian communion consisting of the Church of England and other autocephalous national and regional churches in full communion. The archbishop of Canterbury in England acts as a focus of unity, recognised as ("first among equals"), but does not exercise authority in Anglican provinces outside of the Church of England. Most, but not all, member churches of the communion are the historic national or regional Anglican churches. With approximately 85 -110 million members, it is the third-largest Christian communion after the Roman Catholic and Eastern Orthodox churches globally.
The Anglican Communion was officially and formally organised and recognised as such at the Lambeth Conference in 1867 in London under the leadership of Charles Longley, Archbishop of Canterbury. The churches of the Anglican Communion consider themselves to be part of the one, holy, catholic and apostolic church, with worship being based on the Book of Common Prayer. The traditional origins of Anglican doctrine are summarized in the Thirty-nine Articles (1571) and The Books of Homilies.
As in the Church of England itself, the Anglican Communion includes the broad spectrum of beliefs and liturgical practises found in the Evangelical, Central and Anglo-Catholic traditions of Anglicanism; both the larger Reformed Anglican and the smaller Arminian Anglican theological perspectives have been represented. Each national or regional church is fully independent, retaining its own legislative process and episcopal polity under the leadership of local primates. For many adherents, Anglicanism represents a distinct form of Reformed Protestantism that emerged under the influence of the Reformer Thomas Cranmer, or for yet others, a via media between two branches of Protestantism—Lutheranism and Calvinism—and for others, a denomination that is both Catholic and Reformed.
Most of its members live in the Anglosphere of former British territories. Full participation in the sacramental life of each church is available to all communicant members. Because of their historical link to England (ecclesia anglicana means "English church"), some of the member churches are known as "Anglican", such as the Anglican Church of Canada. Others, for example the Church of Ireland and the Scottish and American Episcopal churches, have official names that do not include "Anglican". Conversely, some churches that do use the name "Anglican" are not part of the communion. These have generally disaffiliated over disagreement with the direction of the communion. |
Anglican Communion | History | History
The Anglican Communion traces much of its growth to the older mission organisations of the Church of England such as the Society for Promoting Christian Knowledge (founded 1698), the Society for the Propagation of the Gospel in Foreign Parts (founded 1701) and the Church Missionary Society (founded 1799). The Church of England (which until the 20th century included the Church in Wales) initially separated from the Roman Catholic Church in 1534 in the reign of Henry VIII, reunited briefly in 1555 under Mary I and then separated again in 1570 under Elizabeth I (the Roman Catholic Church excommunicated Elizabeth I in 1570 in response to the Act of Supremacy 1559).
The Church of England has always thought of itself not as a new foundation but rather as a reformed continuation of the ancient "English Church" (Ecclesia Anglicana) and a reassertion of that church's rights. As such it was a distinctly national phenomenon. The Church of Scotland was formed as a separate church from the Roman Catholic Church as a result of the Scottish Reformation in 1560 and the later formation of the Scottish Episcopal Church began in 1582 in the reign of James VI over disagreements about the role of bishops.
The oldest-surviving Anglican church building outside the British Isles (Britain and Ireland) is St Peter's Church in St. George's, Bermuda, established in 1612 (though the actual building had to be rebuilt several times over the following century). This is also the oldest surviving non-Roman Catholic church in the New World. It remained part of the Church of England until 1978 when the Anglican Church of Bermuda was formed. The Church of England was the established church not only in England, but in its trans-Oceanic colonies. Thus the only member churches of the present Anglican Communion existing by the mid-18th century were the Church of England, its closely linked sister church the Church of Ireland (which also separated from Roman Catholicism under Henry VIII) and the Scottish Episcopal Church which for parts of the 17th and 18th centuries was partially underground (it was suspected of Jacobite sympathies). |
Anglican Communion | Global spread of Anglicanism | Global spread of Anglicanism
thumb|Anglican confirmation at the Mikael Agricola Church in Helsinki, Finland, in June 2013
The enormous expansion in the 18th and 19th centuries of the British Empire brought Anglicanism along with it. At first all these colonial churches were under the jurisdiction of the bishop of London. After the American Revolution, the parishes in the newly independent country found it necessary to break formally from a church whose supreme governor was (and remains) the British monarch. Thus they formed their own dioceses and national church, the Episcopal Church in the United States of America, in a mostly amicable separation.
At about the same time, in the colonies which remained linked to the crown, the Church of England began to appoint colonial bishops. In 1787, Charles Inglis (Bishop of Nova Scotia) was appointed with a jurisdiction over all of British North America; in time several more colleagues were appointed to other cities in present-day Canada. In 1814, a bishop of Calcutta was made; in 1824 the first bishop was sent to the West Indies and in 1836 to Australia. By 1840 there were still only ten colonial bishops for the Church of England; but even this small beginning greatly facilitated the growth of Anglicanism around the world. In 1841, a "Colonial Bishoprics Council" was set up and soon many more dioceses were created.
In time, it became natural to group these into provinces and a metropolitan bishop was appointed for each province. Although it had at first been somewhat established in many colonies, in 1861 it was ruled that, except where specifically established, the Church of England had just the same legal position as any other church. Thus a colonial bishop and colonial diocese was by nature quite a different thing from their counterparts back home. In time bishops came to be appointed locally rather than from England and eventually national synods began to pass ecclesiastical legislation independent of England.
A crucial step in the development of the modern communion was the idea of the Lambeth Conferences (discussed above). These conferences demonstrated that the bishops of disparate churches could manifest the unity of the church in their episcopal collegiality despite the absence of universal legal ties. Some bishops were initially reluctant to attend, fearing that the meeting would declare itself a council with power to legislate for the church; but it agreed to pass only advisory resolutions. These Lambeth Conferences have been held roughly every ten years since 1878 (the second such conference) and remain the most visible coming-together of the whole communion.
The Lambeth Conference of 1998 included what has been seen by Philip Jenkins and others as a "watershed in global Christianity". The 1998 Lambeth Conference considered the issue of the theology of same-sex attraction in relation to human sexuality. At this 1998 conference for the first time in centuries the Christians of developing regions, especially, Africa, Asia and Latin America, prevailed over the bishops of more prosperous countries (many from the US, Canada and the UK) who supported a redefinition of Anglican doctrine. Seen in this light, 1998 is a date that marked the shift from a West-dominated Christianity to one wherein the growing churches of the two-thirds world are predominant. |
Anglican Communion | 21st-century ''de facto'' schisms | 21st-century de facto schisms
Many of the provinces in developed countries have continued to adopt more liberal stances on sexuality and other issues, resulting in a number of de facto schisms, such as the series of splits which led to the creation of the Anglican Church in North America. Many churches are now in full communion with only some other churches but not others, although all churches continue to claim to be part of the Anglican Communion.
On 20 February 2023, following the decision of the Church of England to allow priests to bless same-sex partnerships, ten communion provinces and Anglican realignment churches within the Global South Fellowship of Anglican Churches released a statement stating that they had declared "impaired communion" with the Church of England and no longer recognised Justin Welby as "first among equals" among the bishops of the communion. |
Anglican Communion | Differences and controversies | Differences and controversies
Some effects of the Anglican Communion's dispersed authority have been differences of opinion (and conflicts) arising over divergent practices and doctrines in parts of the communion. Disputes that had been confined to the Church of England could be dealt with legislatively in that realm, but as the communion spread out into new countries and territories, and disparate cultures, controversies often multiplied and intensified. These controversies have generally been of two types: liturgical and social.
Rapid social change and the dissipation of British cultural hegemony over its former colonies contributed to disputes over the role of women, and the parameters of marriage and divorce. In the late 1970s, the Continuing Anglican movement produced a number of new church bodies in opposition to women's ordination, prayer book changes, and the new understandings concerning marriage. |
Anglican Communion | Anglo-Catholicism | Anglo-Catholicism
The first such controversy of note concerned that of the growing influence of the Catholic Revival manifested in the Tractarian and so-called Ritualist controversies of the late 19th and early 20th centuries. This controversy produced the Free Church of England and, in the United States and Canada, the Reformed Episcopal Church. |
Anglican Communion | Abortion and euthanasia | Abortion and euthanasia
While individual Anglicans and member churches within the communion differ in good faith over the circumstances in which abortion should or should not be permitted, Lambeth Conference resolutions have consistently held to a conservative view on the issue. The 1930 conference, the first to be held since the initial legalisation of abortion in Europe (in Russia in 1920), stated:
The 1958 conference's Family in Contemporary Society report affirmed the following position on abortion and was commended by the 1968 conference:
The subsequent Lambeth Conference, in 1978, made no change to this position and commended the need for "programmes at diocesan level, involving both men and women ... to emphasise the sacredness of all human life, the moral issues inherent in clinical abortion, and the possible implications of genetic engineering."
In the context of debates around and proposals for the legalisation of euthanasia and assisted suicide, the 1998 conference affirmed that "life is God-given and has intrinsic sanctity, significance and worth". |
Anglican Communion | Same-sex unions and LGBT clergy | Same-sex unions and LGBT clergy
More recently, disagreements over homosexuality have strained the unity of the communion as well as its relationships with other Christian denominations, leading to another round of withdrawals from the Anglican Communion. Some churches were founded outside the Anglican Communion in the late 20th and early 21st centuries, largely in opposition to the ordination of openly homosexual bishops and other clergy and are usually referred to as belonging to the Anglican realignment movement, or else as "orthodox" Anglicans. These disagreements were especially noted when The Episcopal Church (US) consecrated an openly gay bishop in a same-sex relationship, Gene Robinson, in 2003, which led some Episcopalians to defect and found the Anglican Church in North America (ACNA); then, the debate reignited when the Church of England agreed to allow clergy to enter into same-sex civil partnerships, as long as they remained celibate, in 2005. The Church of Nigeria opposed the Episcopal Church's decision as well as the Church of England's approval for celibate civil partnerships.
According to the BBC, "The more liberal provinces that are open to changing Church doctrine on marriage in order to allow for same-sex unions include Brazil, Canada, New Zealand, Scotland, South India, South Africa, the US and Wales". In 2023, the Church of England announced that it will authorise "prayers of thanksgiving, dedication and for God's blessing for same-sex couples". The Church of England also permits clergy to enter into same-sex civil partnerships. In 2024, the Church of England's General Synod voted to support allowing clergy to enter in civil same-sex marriages. In 2023, the Anglican Church of Southern Africa's bishops approved the drafting of prayers that could be said with same-sex couples and the draft prayers were published for consideration in 2024. The Church of Ireland has no official position on civil unions, and one senior cleric has entered into a same-sex civil partnership. The Church of Ireland recognised that it will "treat civil partners the same as spouses". The Anglican Church of Australia does not have an official position on homosexuality.
The conservative Anglican churches encouraging the realignment movement are more concentrated in the Global South. For example, the Anglican Church of Kenya, the Church of Nigeria and the Church of Uganda have opposed homosexuality. GAFCON, a fellowship of conservative Anglican churches, has appointed "missionary bishops" in response to the disagreements with the perceived liberalisation in the Anglican churches in North America and Europe. In 2023, ten archbishops within the Anglican Communion and two breakaway churches in North America and Brazil from the Global South Fellowship of Anglican Churches (GSFA) declared a state of impaired communion with the Church of England and announced that they would no longer recognise the archbishop of Canterbury as the "first among equals" among the bishops in the Anglican Communion. However, in the same statement, the ten archbishops said that they would not leave the Anglican Communion. In 2024, the GSFA met again establishing "a new structure," no longer recognising the Archbishop of Canterbury "as the de facto leader" of the Anglican Communion, but the GSFA reiterated that they intend to remain in the Anglican Communion.
Debates about social theology and ethics have occurred at the same time as debates on prayer book revision and the acceptable grounds for achieving full communion with non-Anglican churches. |
Anglican Communion | Ecclesiology, polity and ethos | Ecclesiology, polity and ethos
The Anglican Communion has no official legal existence nor any governing structure that might exercise authority over the member churches. There is an Anglican Communion Office in London, under the aegis of the archbishop of Canterbury, but it serves only in a supporting and organisational role. The communion is held together by a shared history, expressed in its ecclesiology, polity and ethos, and also by participation in international consultative bodies.
Three elements have been important in holding the communion together: first, the shared ecclesial structure of the component churches, manifested in an episcopal polity maintained through the apostolic succession of bishops and synodical government; second, the principle of belief expressed in worship, investing importance in approved prayer books and their rubrics; and third, the historical documents and the writings of early Anglican divines that have influenced the ethos of the communion.
Originally, the Church of England was self-contained and relied for its unity and identity on its own history, its traditional legal and episcopal structure, and its status as an established church of the state. As such, Anglicanism was from the outset a movement with an explicitly episcopal polity, a characteristic that has been vital in maintaining the unity of the communion by conveying the episcopate's role in manifesting visible catholicity and ecumenism.
Early in its development following the English Reformation, Anglicanism developed a vernacular prayer book, called the Book of Common Prayer. Unlike other traditions, Anglicanism has never been governed by a magisterium nor by appeal to one founding theologian, nor by an extra-credal summary of doctrine (such as the Westminster Confession of the Presbyterian churches). Instead, Anglicans have typically appealed to the Book of Common Prayer (1662) and its offshoots as a guide to Anglican theology and practise. This has had the effect of inculcating in Anglican identity and confession the principle of ("the law of praying [is] the law of believing").
Protracted conflict through the 17th century, with radical Protestants on the one hand and Roman Catholics who recognised the primacy of the Pope on the other, resulted in an association of churches that was both deliberately vague about doctrinal principles, yet bold in developing parameters of acceptable deviation. These parameters were most clearly articulated in the various rubrics of the successive prayer books, as well as the Thirty-nine Articles of Religion (1563). These articles have historically shaped and continue to direct the ethos of the communion, an ethos reinforced by its interpretation and expansion by such influential early theologians such as Richard Hooker, Lancelot Andrewes and John Cosin.
With the expansion of the British Empire and the growth of Anglicanism outside Great Britain and Ireland, the communion sought to establish new vehicles of unity. The first major expressions of this were the Lambeth Conferences of the communion's bishops, first convened in 1867 by Charles Longley, the archbishop of Canterbury. From the beginning, these were not intended to displace the autonomy of the emerging provinces of the communion, but to "discuss matters of practical interest, and pronounce what we deem expedient in resolutions which may serve as safe guides to future action".Davidson, R. T. (ed.) (1889). The Lambeth Conferences of 1867, 1878, and 1888: With the Official Reports and Resolutions Together with the Sermons Preached at the Conferences. Society for Promoting Christian Knowledge. |
Anglican Communion | Chicago Lambeth Quadrilateral | Chicago Lambeth Quadrilateral
One of the enduringly influential early resolutions of the conference was the so-called Chicago-Lambeth Quadrilateral of 1888. Its intent was to provide the basis for discussions of reunion with the Roman Catholic and Orthodox churches, but it had the ancillary effect of establishing parameters of Anglican identity. It establishes four principles with these words:The Book of Common Prayer of the Episcopal Church, Seabury Press, 1979, p. 877 |
Anglican Communion | Instruments of communion | Instruments of communion
As mentioned above, the Anglican Communion has no international juridical organisation. The archbishop of Canterbury's role is strictly symbolic and unifying and the communion's three international bodies are consultative and collaborative, their resolutions having no legal effect on the autonomous provinces of the communion. Taken together, however, the four do function as "instruments of communion", since all churches of the communion participate in them. In order of antiquity, they are:
thumb|The Chair of St Augustine (the episcopal throne in Canterbury Cathedral, Kent), seat of the archbishop of Canterbury in his role as head of the Anglican Communion
The archbishop of Canterbury functions as the spiritual head of the communion. The archbishop is the focus of unity, since no church claims membership in the communion without being in communion with him. The office is currently vacant.
The Lambeth Conference (first held in 1867) is the oldest international consultation. It is a forum for bishops of the communion to reinforce unity and collegiality through manifesting the episcopate, to discuss matters of mutual concern, and to pass resolutions intended to act as guideposts. It is held roughly every ten years and invitation is by the archbishop of Canterbury.
The Anglican Consultative Council (first met in 1971) was created by a 1968 Lambeth Conference resolution, and meets usually at three-yearly intervals. The council consists of representative bishops, other clergy and laity chosen by the 38 provinces. The body has a permanent secretariat, the Anglican Communion Office, of which the archbishop of Canterbury is president.
The Primates' Meeting (first met in 1979) is the most recent manifestation of international consultation and deliberation, having been first convened by Archbishop Donald Coggan as a forum for "leisurely thought, prayer and deep consultation".Jeremy Morris, The Oxford History of Anglicanism, Volume IV: Global Western Anglicanism, c. 1910–Present (Oxford University Press, 2017), 320–22.
Since there is no binding authority in the Anglican Communion, these international bodies are a vehicle for consultation and persuasion. In recent times, persuasion has tipped over into debates over conformity in certain areas of doctrine, discipline, worship and ethics. The most notable example has been the objection of many provinces of the communion (particularly in Africa and Asia) to the changing acceptance of LGBTQ+ individuals in the North American churches (e.g., by blessing same-sex unions and ordaining and consecrating same-sex relationships) and to the process by which changes were undertaken. (See Anglican realignment)
Those who objected condemned these actions as unscriptural, unilateral, and without the agreement of the communion prior to these steps being taken. In response, the American Episcopal Church and the Anglican Church of Canada answered that the actions had been undertaken after lengthy scriptural and theological reflection, legally in accordance with their own canons and constitutions and after extensive consultation with the provinces of the communion.
The Primates' Meeting voted to request the two churches to withdraw their delegates from the 2005 meeting of the Anglican Consultative Council. Canada and the United States decided to attend the meeting but without exercising their right to vote. They have not been expelled or suspended, since there is no mechanism in this voluntary association to suspend or expel an independent province of the communion. Since membership is based on a province's communion with Canterbury, expulsion would require the archbishop of Canterbury's refusal to be in communion with the affected jurisdictions. In line with the suggestion of the Windsor Report, Rowan Williams (the then archbishop of Canterbury) established a working group to examine the feasibility of an Anglican covenant which would articulate the conditions for communion in some fashion. |
Anglican Communion | Organisation | Organisation |
Anglican Communion | Provinces | Provinces
thumb|upright=3.65|A world map showing the provinces of the Anglican Communion:
The Church of Ireland serves both Northern Ireland and the Republic of Ireland and the Anglican Church of Korea serves South Korea and, theoretically, North Korea. Indian Anglicanism is divided into the Church of North India, and the Church of South India. The Diocese in Europe (formally the Diocese of Gibraltar in Europe), in the Province of Canterbury, is also present in Portugal and Spain. The Episcopal Church, USA-affiliated Convocation of Episcopal Churches in Europe has affiliates in Austria, Belgium, France, Georgia, Germany and Italy.|center
The Anglican Communion consists of forty-two autonomous provinces each with its own primate and governing structure. These provinces may take the form of national churches (such as in Canada, Uganda, or Japan) or a collection of nations (such as the West Indies, Central Africa, or Southeast Asia).
Provinces Territorial Jurisdiction Membership Year Episcopal/Anglican Province of Alexandria Algeria, Djibouti, Egypt, Ethiopia, Eritrea, Libya, Somalia, Tunisia 50,000 2022 Anglican Church in Aotearoa, New Zealand and Polynesia New Zealand, Cook Islands, Fiji, Samoa, Tonga245,301 - 459,7112016-2023 Anglican Church of Australia Australia2,496,273 - 4,865,3282016 - 2021 Church of Bangladesh Bangladesh15,6222016 Anglican Episcopal Church of Brazil Brazil19,400 - 120,0002012 Province of the Anglican Church of Burundi Burundi800,0002016 Anglican Church of Canada Canada294,931 - 1,134,3152022 Church of the Province of Central Africa Botswana, Malawi, Zambia, Zimbabwe900,0002016 Anglican Church in Central America Costa Rica, El Salvador, Guatemala, Nicaragua, Panama13,409 - 35,0002005 Anglican Church of Chile Chile20,0002018 Province of the Anglican Church of the Congo Democratic Republic of the Congo, Republic of Congo500,0002016 Church of England England, Crown Dependencies, Europe7,975,200 - 26,000,0002018 Hong Kong Sheng Kung Hui Hong Kong, Macau29,0002007 Church of the Province of the Indian Ocean Madagascar, Mauritius, Seychelles505,0002016 Church of Ireland Republic of Ireland, Northern Ireland 343,400 2023 Anglican Church in Japan Japan22,0002022 Episcopal Church in Jerusalem and the Middle East Bahrain, Cyprus, Iran, Iraq, Israel, Jordan, Kuwait, Lebanon, Oman, Palestine, Qatar, Saudi Arabia, Syria, United Arab Emirates, Yemen39,8822016 Anglican Church of Kenya Kenya5,000,0002016 Anglican Church of Korea South Korea, North Korea65,0002016 Anglican Church of Melanesia New Caledonia, Solomon Islands, Vanuatu200,0002016 Anglican Church of Mexico Mexico22,000 - 100,0002016 Anglican Church of Mozambique and Angola Angola and Mozambique653,2002022 Church of the Province of Myanmar Myanmar62,0002016 Church of Nigeria Nigeria6,897,240 - 22,000,0002010-2016 Church of North India Bhutan, India 1,250,000 - 2,200,000 2020 Church of Pakistan Pakistan500,0002014 Anglican Church of Papua New Guinea Papua New Guinea233,2282011 Episcopal Church in the Philippines Philippines125,0002016 Anglican Church of Rwanda Rwanda383,904 - 1,000,0002010-2016 Scottish Episcopal Church Scotland23,503 - 53,553 2016 - 2023 Anglican Church of South America Argentina, Bolivia, Paraguay, Peru, Uruguay22,5002023 Church of the Province of South East Asia Brunei, Cambodia, Indonesia, Laos, Malaysia, Nepal, Singapore, Thailand, Vietnam98,0002017 Church of South India India, Sri Lanka4,500,0002022 Province of the Episcopal Church of South Sudan South Sudan3,500,0002014 Anglican Church of Southern Africa Eswatini, Lesotho, Namibia, Saint Helena, South Africa2,300,000 - 4,000,0002016 Province of the Episcopal Church of Sudan Sudan1,000,0002014 Anglican Church of Tanzania Tanzania2,000,0002016 Church of Uganda Uganda13,311,8012024 Episcopal Church British Virgin Islands, Colombia, Cuba, Dominican Republic, Ecuador, Europe, Guam, Haiti, Honduras, Northern Mariana Islands, Puerto Rico, Taiwan, United States, United States Virgin Islands, Venezuela1,547,779 - 2,405,0002016-2023 Church in Wales Wales 45,759 - 84,0002016 - 2018Church in Wales will spend £10m to 'breathe new life' into its churches 20 May 2018 WalesOnline Church of the Province of West Africa Cameroon, Cape Verde, Gambia, Ghana, Guinea, Liberia, Senegal, Sierra Leone300,0002016 Church in the Province of the West Indies Anguilla, Antigua and Barbuda, Aruba, Bahamas, Barbados, Belize, Cayman Islands, Dominica, Grenada, Guyana, Jamaica, Montserrat, Saba, Saint Barthélemy, Saint Kitts and Nevis, Saint Lucia, Saint Martin, Saint Vincent and the Grenadines, Sint Eustatius, Trinidad and Tobago, Turks and Caicos Islands770,0002016 Anglican Communion Global 59,149,979 - 100,180,193 2006-2023 |
Anglican Communion | Extraprovincial churches | Extraprovincial churches
In addition to the forty-two provinces, there are five extraprovincial churches under the metropolitical authority of the archbishop of Canterbury.
Provinces Territorial Jurisdiction Membership Year Anglican Church of Bermuda Bermuda9,647 2010 Church of Ceylon Sri Lanka50,000 2006 Parish of the Falkland Islands Falkland Islands - - Lusitanian Catholic Apostolic Evangelical Church Portugal5,000 2010 Spanish Reformed Episcopal Church Spain5,000 2010 |
Anglican Communion | Former provinces | Former provinces
Province Territorial Jurisdiction Year Established Year Dissolved Chung Hua Sheng Kung Hui China 1912 1949 (1958) Church of Hawaii Hawaii 1862 1902 Church of India, Pakistan, Burma and Ceylon Bangladesh, India, Myanmar, Pakistan, Sri Lanka 1930 1970 Protestant Episcopal Church in the Confederate States of America Confederate States of America 1861 1865 United Church of England and Ireland England, Wales, Ireland 1800 1871 |
Anglican Communion | New provinces in formation | New provinces in formation
In September 2020, the Archbishop of Canterbury announced that he had asked the bishops of the Church of Ceylon to begin planning for the formation of an autonomous province of Ceylon, so as to end his current position as metropolitan of the two dioceses in that country. |
Anglican Communion | Churches in full communion | Churches in full communion
In addition to other member churches, the churches of the Anglican Communion are in full communion with the Old Catholic churches of the Union of Utrecht and the Scandinavian Lutheran churches of the Porvoo Communion in Europe, the India-based Malankara Mar Thoma Syrian and Malabar Independent Syrian churches and the Philippine Independent Church, also known as the Aglipayan Church. |
Anglican Communion | Ecumenical relations | Ecumenical relations |
Anglican Communion | Historic episcopate | Historic episcopate
The churches of the Anglican Communion have traditionally held that ordination in the historic episcopate is a core element in the validity of clerical ordinations. The Roman Catholic Church, however, does not recognise Anglican orders (see Apostolicae curae). Some Eastern Orthodox churches have issued statements to the effect that Anglican orders could be accepted, yet have still reordained former Anglican clergy; other Eastern Orthodox churches have rejected Anglican orders altogether. Orthodox bishop Kallistos Ware explains this apparent discrepancy as follows: |
Anglican Communion | See also | See also
Acts of Supremacy
English Reformation
Dissolution of the Monasteries
Ritualism in the Church of England
Apostolicae curae
Affirming Catholicism
Anglican ministry
Anglo-Catholicism
British Israelism
Church Society
Church's Ministry Among Jewish People
Compass rose
Evangelical Anglicanism
Flag of the Anglican Communion
Liberal Anglo-Catholicism
List of the largest Protestant bodies
Reform (Anglican)
Anglican Use |
Anglican Communion | Notes | Notes |
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