the two most abundant elements in earth 's atmosphere today are
nitrogen oxygen
2385709
atmosphere is nitrogen (78.1%), oxygen (20.9%), argon (0.96%), followed by (in uncertain order) carbon and hydrogen because water vapor and carbon dioxide, which represent most of these two elements in the air, are variable components. Sulfur, phosphorus, and all other elements are present in significantly lower proportions. According to the abundance curve graph (above right), argon, a significant if not major component of the atmosphere, does not appear in the crust at all. This is because the atmosphere has a far smaller mass than the crust, so argon remaining in the crust contributes little to mass-fraction there, while at the
Abundance of the chemical elements
462861
timescale. In addition, they remain in a bloated proto-white dwarf stage for up to 2 Gyr before they reach the cooling track. Although most white dwarfs are thought to be composed of carbon and oxygen, spectroscopy typically shows that their emitted light comes from an atmosphere which is observed to be either hydrogen or helium dominated. The dominant element is usually at least 1,000 times more abundant than all other elements. As explained by Schatzman in the 1940s, the high surface gravity is thought to cause this purity by gravitationally separating the atmosphere so that heavy elements are below and
White dwarf
2946707
minerals of the crust and mantle (99.5% by weight). The Earth's atmosphere, hydrosphere and biosphere together weigh less than 0.05% of the Earth's total mass. Oxygen is one of the most abundant elements on Earth and represents a large portion of each main reservoir: Movement of oxygen between the reservoirs is facilitated in large part by the presence of atmospheric free oxygen. The main source of atmospheric free oxygen is photosynthesis, which produces sugars and free oxygen from carbon dioxide and water: Photosynthesizing organisms include the plant life of the land areas as well as the phytoplankton of the oceans.
Oxygen cycle
2385707
have larger ionic radii) and therefore more strongly concentrated in the continental crust than the heavier rare earth elements. In most rare earth ore deposits, the first four rare earth elements – lanthanum, cerium, praseodymium, and neodymium – constitute 80% to 99% of the total amount of rare earth metal that can be found in the ore. The mass-abundance of the eight most abundant elements in the Earth's mantle (see main article above) is approximately: oxygen 45%, magnesium 23%, silicon 22%, iron 5.8%, calcium 2.3%, aluminum 2.2%, sodium 0.3%, potassium 0.3%. The mantle differs in elemental composition from the crust
Abundance of the chemical elements
16103829
of early Earth (the first billion years) was drastically different from its current state. Initially, hydrogen and helium compounds dominated the atmosphere. However, given the relatively small size of these elements and the warmer temperature of Earth compared to other planets at the time, most of these lighter compounds escaped, leaving behind an atmosphere composed mainly of methane, nitrogen, oxygen and ammonia with small concentrations of hydrogen compounds and other gases. The atmosphere was transitioning from a reduction atmosphere (an atmosphere that inhibits oxidation) to one of oxidation, similar to our current atmosphere. The origin of life on Earth has
Paleolightning
305243
the third most abundant chemical element in the universe, after hydrogen and helium. About 0.9% of the Sun's mass is oxygen. Oxygen constitutes 49.2% of the Earth's crust by mass as part of oxide compounds such as silicon dioxide and is the most abundant element by mass in the Earth's crust. It is also the major component of the world's oceans (88.8% by mass). Oxygen gas is the second most common component of the Earth's atmosphere, taking up 20.8% of its volume and 23.1% of its mass (some 10 tonnes). Earth is unusual among the planets of the Solar System
Oxygen
9240
amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements. The alkali metals, due to their high reactivity, do not occur naturally in pure form in nature. They are lithophiles and therefore remain close to the Earth's surface because they combine readily with oxygen and so associate strongly with silica, forming relatively low-density minerals that do not sink down into the Earth's core. Potassium, rubidium and caesium are also incompatible elements due to their large ionic radii. Sodium and potassium are very abundant in earth, both being among the ten most common elements in Earth's crust; sodium makes
Alkali metal
280664
component of nucleic acids, amino acids and thus proteins, and the energy-carrying molecule adenosine triphosphate and is thus vital to all life on Earth. Nitrogen is the most common pure element in the earth, making up 78.1% of the entire volume of the atmosphere. Despite this, it is not very abundant in Earth's crust, making up only 19 parts per million of this, on par with niobium, gallium, and lithium. The only important nitrogen minerals are nitre (potassium nitrate, saltpetre) and sodanitre (sodium nitrate, Chilean saltpetre). However, these have not been an important source of nitrates since the 1920s, when
Nitrogen
331477
Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments. In plants, these proteins are held inside organelles called chloroplasts, which are most abundant in leaf cells, while in bacteria they are embedded in the plasma membrane. In these light-dependent reactions, some energy is used to strip electrons from suitable substances, such as water, producing oxygen gas. The hydrogen freed by the splitting
Photosynthesis
10540
in the interstellar gas. Overall, the Earth is about 1.59% aluminium by mass (seventh in abundance by mass). Aluminium occurs in greater proportion in the Earth than in the Universe because aluminium easily forms the oxide and becomes bound into rocks and aluminium stays in the Earth's crust while less reactive metals sink to the core. In the Earth's crust, aluminium is the most abundant (8.3% by mass) metallic element 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
Aluminium
12431213
S-type star An S-type star (or just S star) is a cool giant with approximately equal quantities of carbon and oxygen in its atmosphere. The class was originally defined in 1922 by Paul Merrill for stars with unusual absorption lines and molecular bands now known to be due to s-process elements. The bands of zirconium monoxide (ZrO) are a defining feature of the S stars. The carbon stars have more carbon than oxygen in their atmospheres. In most stars, such as class M giants, the atmosphere is richer in oxygen than carbon and they are referred to as "oxygen-rich stars".
S-type star
69034
Chemical element A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or "Z"). For example, the atomic number of oxygen is 8, so the element oxygen consists of all atoms which have exactly 8 protons. 118 elements have been identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. There are 80 elements that have at least one stable isotope and 38 that have exclusively radionuclides, which decay over time into other elements. Iron is the most abundant
Chemical element
4550155
Trace gas The most abundant gases in the atmosphere are nitrogen (78.1%), oxygen (20.9%), and argon (0.934%). Combined, oxygen, argon, and nitrogen make up 99.934% of the gases in the atmosphere (not including water vapor). The other gases that are not part of the 99.934% of the atmosphere are called trace gases. The abundance of a trace gas can range from a few parts per trillion (ppt) by volume to several hundred parts per million by volume (ppmv). When a trace gas is added into the atmosphere, that process is called a "source". There are two possible types of sources
Trace gas
2385708
in having a great deal more magnesium and significantly more iron, while having much less aluminum and sodium. Due to mass segregation, the core of the Earth is believed to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements. The most abundant elements in the ocean by proportion of mass in percent are oxygen (85.84), hydrogen (10.82), chlorine (1.94), sodium (1.08), magnesium (0.1292), sulfur (0.091), calcium (0.04), potassium (0.04), bromine (0.0067), carbon (0.0028), and boron (0.00043). The order of elements by volume-fraction (which is approximately molecular mole-fraction) in the
Abundance of the chemical elements
10271067
other trace elements, including compounds based on hydrogen, nitrogen, sulfur, carbon, and oxygen. The atmosphere of Venus is much hotter and denser than that of Earth, though shallower. As greenhouse gases warm a lower atmosphere, they cool the upper atmosphere, leading to compact thermospheres. By some definitions, Venus has no stratosphere. The troposphere begins at the surface and extends up to an altitude of 65 kilometres (an altitude at which the mesosphere has already been reached on Earth). At the top of the troposphere, temperature and pressure reach Earth-like levels. Winds at the surface are a few metres per second,
Extraterrestrial atmosphere
305210
Oxygen Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula . Diatomic oxygen gas constitutes 20.8% of the Earth's atmosphere. As compounds including oxides, the element
Oxygen
5345779
melting in basalt. Earth is often described as having had three atmospheres. The first atmosphere, captured from the solar nebula, was composed of light (atmophile) elements from the solar nebula, mostly hydrogen and helium. A combination of the solar wind and Earth's heat would have driven off this atmosphere, as a result of which the atmosphere is now depleted of these elements compared to cosmic abundances. After the impact which created the moon, the molten Earth released volatile gases; and later more gases were released by volcanoes, completing a second atmosphere rich in greenhouse gases but poor in oxygen. Finally,
History of Earth
402866
Earth, plant life could also be brought in. This would accelerate the production of oxygen, which theoretically would make the planet eventually able to support animal life. In many respects, Mars is the most Earth-like planet in the Solar System. It is thought that Mars once had a more Earth-like environment early in its history, with a thicker atmosphere and abundant water that was lost over the course of hundreds of millions of years. The exact mechanism of this loss is still unclear, though three mechanisms in particular seem likely: First, whenever surface water is present, carbon dioxide () reacts
Terraforming
3419825
are the feed gas and the mixed refrigerant. The chief source of inefficiency lies in the heat exchange train during the liquefaction process. Cryogenic fuel Cryogenic fuels are fuels that require storage at extremely low temperatures in order to maintain them in a liquid state. These fuels are used in machinery that operates in space (e.g. rocket ships and satellites) because ordinary fuel cannot be used there, due to absence of an environment that supports combustion (on Earth, oxygen is abundant in the atmosphere, whereas in human-explorable space, oxygen is virtually non-existent) and space is a vacuum. Cryogenic fuels most
Cryogenic fuel
305306
gold or platinum) are prized because they resist direct chemical combination with oxygen, and substances like gold(III) oxide must be generated by indirect routes. Two independent pathways for corrosion of elements are hydrolysis and oxidation by oxygen. The combination of water and oxygen is even more corrosive. Virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen (or simply air), some elements— sodium—react rapidly, to give the hydroxides. In part for this reason, alkali and alkaline earth metals are not found in nature in their metallic, i.e., native, form.
Oxide
250334
the magnesium is expelled into the interstellar medium where it may recycle into new star systems. Magnesium is the eighth most abundant element in the Earth's crust and the fourth most common element in the Earth (after iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet's mantle. It is the third most abundant element dissolved in seawater, after sodium and chlorine. Magnesium occurs naturally only in combination with other elements, where it invariably has a +2 oxidation state. The free element (metal) can be produced artificially, and is highly reactive (though
Magnesium
3419818
Cryogenic fuel Cryogenic fuels are fuels that require storage at extremely low temperatures in order to maintain them in a liquid state. These fuels are used in machinery that operates in space (e.g. rocket ships and satellites) because ordinary fuel cannot be used there, due to absence of an environment that supports combustion (on Earth, oxygen is abundant in the atmosphere, whereas in human-explorable space, oxygen is virtually non-existent) and space is a vacuum. Cryogenic fuels most often constitute liquefied gases such as liquid hydrogen. Some rocket engines use regenerative cooling, the practice of circulating their cryogenic fuel around the
Cryogenic fuel
2385709
atmosphere is nitrogen (78.1%), oxygen (20.9%), argon (0.96%), followed by (in uncertain order) carbon and hydrogen because water vapor and carbon dioxide, which represent most of these two elements in the air, are variable components. Sulfur, phosphorus, and all other elements are present in significantly lower proportions. According to the abundance curve graph (above right), argon, a significant if not major component of the atmosphere, does not appear in the crust at all. This is because the atmosphere has a far smaller mass than the crust, so argon remaining in the crust contributes little to mass-fraction there, while at the
Abundance of the chemical elements
253019
stacking groups of three layers ("abcabcabc"). Analogues to linked silica tetrahedra include SO (sulfate), PO (phosphate), AsO (arsenate), and VO (vanadate). The non-silicates have great economic importance, as they concentrate elements more than the silicate minerals do. The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth's crust is composed of these minerals. The two main constituents of silicates are silicon and oxygen, which are the two most abundant elements in the Earth's crust. Other common elements in silicate minerals correspond to other common
Mineral
405923
Melting is possible only in an inert atmosphere or in a vacuum. At , it combines with chlorine. It also reacts with the other halogens and absorbs hydrogen. Titanium is one of the few elements that burns in pure nitrogen gas, reacting at to form titanium nitride, which causes embrittlement. Because of its high reactivity with oxygen, nitrogen, and some other gases, titanium filaments are applied in titanium sublimation pumps as scavengers for these gases. Such pumps inexpensively and reliably produce extremely low pressures in ultra-high vacuum systems. Titanium is the ninth-most abundant element in Earth's crust (0.63% by mass)
Titanium
311836
studies because potassium is a macronutrient required for life. Potassium is formed in supernovae by nucleosynthesis from lighter atoms. Potassium is principally created in Type II supernovae via an explosive oxygen-burning process. is also formed in s-process nucleosynthesis and the neon burning process. Potassium is the 20th most abundant element in the solar system and the 17th most abundant element by weight in the earth. It makes up about 2.6% of the weight of the earth's crust and is the seventh most abundant element in the crust. The potassium concentration in seawater is 0.39 g/L (0.039 wt/v%), about one twenty-seventh
Potassium
462267
that water has been prevalent in the universe for nearly its entire existence". Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundance in other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Based on models of the formation and evolution of the Solar System and that of other star systems, most other planetary systems are likely to have similar ingredients. Water is present as vapor in: Liquid water is present on Earth, covering 71% of its surface. Liquid water is also occasionally
Water
16198580
crust, besides silicon and oxygen, are iron, magnesium, aluminum, calcium, and potassium. These elements are major components of the minerals comprising igneous rocks. The elements titanium, chromium, manganese, sulfur, phosphorus, sodium, and chlorine are less abundant but are still important components of many accessory minerals in rocks and of secondary minerals (weathering products) in the dust and soils (the regolith). Hydrogen is present as water (HO) ice and in hydrated minerals. Carbon occurs as carbon dioxide (CO) in the atmosphere and sometimes as dry ice at the poles. An unknown amount of carbon is also stored in carbonates. Molecular nitrogen
Composition of Mars
6694589
more than any other element, with almost ten million compounds described to date, and yet that number is but a fraction of the number of theoretically possible compounds under standard conditions. For this reason, carbon has often been referred to as the "king of the elements". Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth enables this element to serve
Carbon-based life
361636
metre, but as viewed through Earth's atmosphere, this is lowered to about 1.44 Gcd/m. However, the luminance is not constant across the disk of the Sun (limb darkening). The Sun is composed primarily of the chemical elements hydrogen and helium. At this time in the Sun's life, they account for 74.9% and 23.8% of the mass of the Sun in the photosphere, respectively. All heavier elements, called "metals" in astronomy, account for less than 2% of the mass, with oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%) being the most abundant. The Sun's original
Sun
874539
a low electrical conductivity of 10 to 10 S·cm. Graphite has an electrical conductivity of 3 × 10 S·cm, a figure more characteristic of a metal. Phosphorus, sulfur, arsenic, selenium, antimony, and bismuth also have less stable allotropes that display different behaviours. The table gives crustal abundances of the elements commonly to rarely recognised as metalloids. Some other elements are included for comparison: oxygen and xenon (the most and least abundant elements with stable isotopes); iron and the coinage metals copper, silver, and gold; and rhenium, the least abundant stable metal (aluminium is normally the most abundant metal). Various abundance
Metalloid
10511
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
Atom
7683566
its development, and that its pressure supported abundant liquid water at the surface. Although water appears to have once been present on the Martian surface, ground ice currently exists from mid-latitudes to the poles. The soil and atmosphere of Mars contain many of the main elements crucial to life, including sulfur, nitrogen, hydrogen, oxygen, phosphorus and carbon. Any climate change induced in the near term is likely to be driven by greenhouse warming produced by an increase in atmospheric carbon dioxide () and a consequent increase in atmospheric water vapor. These two gases are the only likely sources of greenhouse
Terraforming of Mars
15830760
and of the temperature T at which the gaseous pressure is equal one atmosphere is Q/T = 32. This law can be applied to such cases as sublimation and dissociation of calcium carbonate and can predict whether a chemical reaction will proceed and whether it will be reversible. At the Sorbonne, Matignon mostly worked on rare-earth elements. He was heating the metal oxide with magnesium to produce the pure metal in an atmosphere of a certain gas, and demonstrated that most rare earths easily react with nitrogen and absorb hydrogen. He also studied the chemistry of numerous rare-earth salts and
Camille Matignon
2385705
earth elements is a historical misnomer. The persistence of the term reflects unfamiliarity rather than true rarity. The more abundant rare earth elements are similarly concentrated in the crust compared to commonplace industrial metals such as chromium, nickel, copper, zinc, molybdenum, tin, tungsten, or lead. The two least abundant rare earth elements (thulium and lutetium) are nearly 200 times more common than gold. However, in contrast to the ordinary base and precious metals, rare earth elements have very little tendency to become concentrated in exploitable ore deposits. Consequently, most of the world's supply of rare earth elements comes from only
Abundance of the chemical elements
280113
numbers increase. Helium is the most common element in the universe after hydrogen, with a mass fraction of about 24%. Most of the helium in the universe was formed during Big Bang nucleosynthesis, but the amount of helium is steadily increasing due to the fusion of hydrogen in stellar nucleosynthesis (and, to a very slight degree, the alpha decay of heavy elements). Abundances on Earth follow different trends; for example, helium is only the third most abundant noble gas in the atmosphere. The reason is that there is no primordial helium in the atmosphere; due to the small mass of
Noble gas
374271
Sulfur Sulfur or sulphur is a chemical element with symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S. Elemental sulfur is a bright yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, and the noble gases. Sulfur is the tenth most common element by mass in the universe, and the fifth most common on Earth. Though sometimes found in pure, native form, sulfur on Earth usually occurs as sulfide and sulfate minerals. Being abundant
Sulfur
12531587
nuclides include 32 nuclides with very long half-lives (over 100 million years) and 253 that are formally considered as "stable nuclides", because they have not been observed to decay. In most cases, for obvious reasons, if an element has stable isotopes, those isotopes predominate in the elemental abundance found on Earth and in the Solar System. However, in the cases of three elements (tellurium, indium, and rhenium) the most abundant isotope found in nature is actually one (or two) extremely long-lived radioisotope(s) of the element, despite these elements having one or more stable isotopes. Theory predicts that many apparently "stable"
Isotope
165440
the Earth's heterosphere, a part of the upper atmosphere, helium and other lighter gases are the most abundant elements. Most helium on Earth is a result of radioactive decay. Helium is found in large amounts in minerals of uranium and thorium, including cleveite, pitchblende, carnotite and monazite, because they emit alpha particles (helium nuclei, He) to which electrons immediately combine as soon as the particle is stopped by the rock. In this way an estimated 3000 metric tons of helium are generated per year throughout the lithosphere. In the Earth's crust, the concentration of helium is 8 parts per billion.
Helium
1288693
produced by supernova nucleosynthesis or the s-process in asymptotic giant branch stars. In nature, spontaneous fission of uranium-238 produces trace amounts of radioactive promethium, but most promethium is synthetically produced in nuclear reactors. Due to their chemical similarity, the concentrations of rare earths in rocks are only slowly changed by geochemical processes, making their proportions useful for geochronology and dating fossils. Rare-earth element cerium is actually the 25th most abundant element in Earth's crust, having 68 parts per million (about as common as copper). Only the highly unstable and radioactive promethium "rare earth" is quite scarce. The rare-earth elements are
Rare-earth element
482506
earth's crust at a concentration of two to six parts per million (ppm), much of which is in soils, where it has a concentration of six ppm. Beryllium is one of the rarest elements in seawater, even rarer than elements such as scandium, with a concentration of 0.2 parts per trillion. However, in freshwater, beryllium is somewhat more common, with a concentration of 0.1 parts per billion. Magnesium and calcium are very common in the earth's crust, being respectively the fifth- eighth-most-abundant elements. None of the alkaline earth metals are found in their elemental state. Common magnesium--containing minerals are carnallite,
Alkaline earth metal
511360
Mg and Ca, dominate in the Earth's crust, forming silicates and other oxides. "Siderophile" elements (Fe, Co, Ni, Pt, Re, Os) have an affinity for iron and tend to concentrate in the core. "Chalcophile" elements (Cu, Ag, Zn, Pb, S) form sulfides; and "atmophile" elements (O, N, H and noble gases) dominate the atmosphere. Within each group, some elements are refractory, remaining stable at high temperatures, while others are volatile, evaporating more easily, so heating can separate them. The chemical composition of the Earth and other bodies is determined by two opposing processes: differentiation and mixing. In the Earth's mantle,
Geochemistry
1288678
other important rare earth minerals, and uranium and decay products are found in others. Both series of elements begin on the periodic table in group 3 under yttrium and scandium. The 17 rare-earth elements are cerium (Ce), dysprosium (Dy), erbium (Er), europium (Eu), gadolinium (Gd), holmium (Ho), lanthanum (La), lutetium (Lu), neodymium (Nd), praseodymium (Pr), promethium (Pm), samarium (Sm), scandium (Sc), terbium (Tb), thulium (Tm), ytterbium (Yb), and yttrium (Y). Despite their name, rare-earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68
Rare-earth element
1288691
yttrium group was further split into the erbium group (dysprosium, holmium, erbium, and thulium) and the ytterbium group (ytterbium and lutetium), but today the main grouping is between the cerium and the yttrium groups. Today, the rare-earth elements are classified as light or heavy rare-earth elements, rather than in cerium and yttrium groups. The classification of rare-earth elements is inconsistent between authors. The most common distinction between rare-earth elements is made by atomic numbers; those with low atomic numbers are referred to as light rare-earth elements (LREE), those with high atomic numbers are the heavy rare-earth elements (HREE), and those
Rare-earth element
406115
since decayed and no longer contribute. In the Earth's crust, thorium is much more abundant: with an abundance of 8.1 parts per million (ppm), it is one of the most abundant of the heavy elements, almost as abundant as lead (13 ppm) and more abundant than tin (2.1 ppm). This is because thorium is likely to form oxide minerals that do not sink into the core; it is classified as a lithophile. Common thorium compounds are also poorly soluble in water. Thus, even though the Earth contains the same abundances of the elements as the Solar System as a whole,
Thorium
1957047
is classified as a volatile, because most of it is liquid or gas, even though it does exist as a solid compound on the surface. Because all atmophile elements are either gases or form volatile hydrides, atmophile elements are "strongly depleted" on earth as a whole relative to their solar abundances owing to losses from the atmosphere during the formation of the Earth. The heavier noble gases (krypton, xenon) are the rarest stable elements on Earth. Goldschmidt classification The Goldschmidt classification, developed by Victor Goldschmidt (1888-1947), is a geochemical classification which groups the chemical elements within the Earth according to
Goldschmidt classification
20342604
the mantle and crust. During the formation of the Earth, the two elements tended not be fractionated into the core during core formation, i.e. not concentrated in the core, unlike siderophile elements (iron-loving elements). Lu and Hf are also refractory elements, meaning they quickly condensed from the protoplanetary disk to form the solid part of Earth, as opposed to volatile elements. The two elements as a result would not be found in Earth's early atmosphere. Due to these characteristics, the two elements are relatively stationary throughout planetary evolution and are thought to retain the isotopic abundance characteristics of primitive planetary
Lutetium–hafnium dating
13612438
be combined to give the total concentration of cosmogenic radionuclides in a sample as a function of age. The two most frequently measured cosmogenic nuclides are beryllium-10 and aluminum-26. These nuclides are particularly useful to geologists because they are produced when cosmic rays strike oxygen-16 and silicon-28, respectively. The parent isotopes are the most abundant of these elements, and are common in crustal material, whereas the radioactive daughter nuclei are not commonly produced by other processes. As oxygen-16 is also common in the atmosphere, the contribution to the beryllium-10 concentration from material deposited rather than created "in situ" must be
Surface exposure dating
4290225
as Tb, Ho, Tm, Lu) each being present at about the 1% level. Dysprosium is usually the most abundant of the even-numbered heavies, and holmium is the most abundant of the odd-numbered heavies. The lightest lanthanides are generally better represented in monazite while the heaviest lanthanides are in xenotime. Xenotime Xenotime is a rare-earth phosphate mineral, the major component of which is yttrium orthophosphate (YPO). It forms a solid solution series with chernovite-(Y) (YAsO) and therefore may contain trace impurities of arsenic, as well as silicon dioxide and calcium. The rare-earth elements dysprosium, erbium, terbium and ytterbium, as well as
Xenotime
12982478
biodiversity and human livelihoods. At current emission rates temperatures could increase by 2 °C, which the United Nations' IPCC designated as the upper limit to avoid "dangerous" levels, by 2036. Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth. In order, the most abundant greenhouse gases in Earth's atmosphere are: Atmospheric concentrations are determined by the balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound or absorption by bodies of water).
Greenhouse gas
261924
lighter transition metals) are the most abundant elements on earth, in the solar system, and in the universe. They are sometimes also called the representative elements. Group 12 elements are often considered to be transition metals; however, zinc (Zn), cadmium (Cd), and mercury (Hg) share some properties of both groups, and many scientists believe they should be included in the main group. Occasionally, even the group 3 elements as well as the lanthanides and actinides have been included, because especially the group 3 elements and lanthanides are electropositive elements with only one main oxidation state like the group 1 and
Main-group element
6161803
at rest in S′, so its worldline is the ct′-axis. The upper atmosphere is at rest in S, so its worldline is the ct-axis. Upon the axes of x and x′, all events are present that are simultaneous with A in S and S′, respectively. The muon and Earth are meeting at D. As the Earth is at rest in S, its worldline (identical with the lower atmosphere) is drawn parallel to the ct-axis, until it intersects the axes of x′ and x. Time: The interval between two events present on the worldline of a single clock is called proper
Experimental testing of time dilation
2699437
regia. Iridium was discovered in a very similar way in 1804 by Smithson Tennant. Meitnerium was discovered in 1982 by bombarding bismuth-209 with iron-58. All group 9 elements are relatively rare in the earth's crust, with the most abundant, cobalt, only accounting for 0.0029% of the Earth's crust. Rhodium and iridium are two of the rarest naturally occurring elements in the earth, only found in platinum ores. Meitnerium has only been produced in nuclear reactors and has never been observed in nature nor isolated in pure form. Cobalt is an essential trace nutrient to all animals, found in vitamin B-12.
Group 9 element
253053
and phosphorus is replaced by antimony, arsenic, or vanadium. The most common phosphate is the apatite group; common species within this group are fluorapatite (Ca(PO)F), chlorapatite (Ca(PO)Cl) and hydroxylapatite (Ca(PO)(OH)). Minerals in this group are the main crystalline constituents of teeth and bones in vertebrates. The relatively abundant monazite group has a general structure of ATO, where T is phosphorus or arsenic, and A is often a rare-earth element (REE). Monazite is important in two ways: first, as a REE "sink", it can sufficiently concentrate these elements to become an ore; secondly, monazite group elements can incorporate relatively large amounts
Mineral
3805201
Helium-4 Helium-4 (' or ') is a non-radioactive isotope of the element helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists of two protons and two neutrons. Alpha decay of heavy elements in the Earth's crust is the source of most naturally occurring helium-4 on Earth. While it is also produced by nuclear fusion in stars, most helium-4 in the Sun and in the universe is thought to have been produced by the Big
Helium-4
422764
Tritium Tritium ( or ; symbol ' or ', also known as hydrogen-3) is a radioactive isotope of hydrogen. The nucleus of tritium (sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of protium (by far the most abundant hydrogen isotope) contains one proton and no neutrons. Naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays. It can be produced by irradiating lithium metal or lithium-bearing ceramic pebbles in a nuclear reactor. Tritium is used as a radioactive tracer, in radioluminescent light sources
Tritium
9530690
and potassium, which are not found in the atmospheres of Earth, Mars, or Venus. At sea level on Earth, each cubic centimeter of the atmosphere contains approximately molecules; by comparison the lunar atmosphere contains fewer than molecules in the same volume. On Earth, this is considered to be a very good vacuum. In fact, the density of the atmosphere at the Moon's surface is comparable to the density of the outermost fringes of Earth's atmosphere, where the International Space Station orbits. The elements sodium and potassium have been detected in the Moon's atmosphere using Earth-based spectroscopic methods, whereas the isotopes
Atmosphere of the Moon
20750028
research group explores the concept of “modern alchemy”, whereby ligand design is used to transmute the reactivity of earth-abundant metals to mimic, or ideally surpass, the performance of precious metals. His group tackles pharmaceutically- and industrially-relevant problems using a combination of synthetic, spectroscopic, physical characterization and computational methods. The major research areas in his laboratory are catalysis with Earth-abundant metals, dinitrogen functionalization, and the interconversion of ammonia with its elements. The core of Chirik’s Earth-abundant metal catalysis program is the understanding and manipulation of electron flow, and its application to solving modern problems. Development efforts are specifically geared towards problems
Paul Chirik
1288679
parts per million, more abundant than copper. They are not especially rare, but they tend to occur together in nature and are difficult to separate from one another. However, because of their geochemical properties, rare-earth elements are typically dispersed and not often found concentrated as rare-earth minerals in economically exploitable ore deposits. The first such mineral discovered (1787) was gadolinite, a mineral composed of cerium, yttrium, iron, silicon, and other elements. This mineral was extracted from a mine in the village of Ytterby in Sweden; four of the rare-earth elements bear names derived from this single location. A table listing
Rare-earth element
16171870
soot is produced from two high-purity graphite electrodes by igniting an arc discharge between them in an inert atmosphere (helium gas). Alternatively, soot is produced by laser ablation of graphite or pyrolysis of aromatic hydrocarbons. C, C and C are available commercially. In the table, N represents the number of possible isomers within the "isolated pentagon rule", which states that two pentagons in a fullerene should not share edges. Symmetry is specified for the most experimentally abundant form(s), and <nowiki>*</nowiki> marks symmetries with more than one chiral form. When C or C crystals are grown from toluene solution they have
Higher fullerenes
1294707
Aluminium occurs widely on earth, and indeed is the third most abundant element in the Earth's crust (8.3%). Gallium is found in the earth with an abundance of 13 ppm. Indium is the 61st most abundant element in the earth's crust, and thallium is found in moderate amounts throughout the planet. Nihonium is never found in nature and therefore is termed a synthetic element. Several group 13 elements have biological roles in the ecosystem. Boron is a trace element in humans and is essential for some plants. Lack of boron can lead to stunted plant growth, while an excess can
Boron group
12425519
molecules to Earth. Amino acids which were formed extraterrestrially may also have arrived on Earth via comets. It is estimated that during the Late Heavy Bombardment, meteorites may have delivered up to five million tons of organic prebiotic elements to Earth per year. Polycyclic aromatic hydrocarbons (PAH) are the most common and abundant of the known polyatomic molecules in the observable universe, and are considered a likely constituent of the primordial sea. In 2010, PAHs, along with fullerenes (or "buckyballs"), have been detected in nebulae. In March 2015, NASA scientists reported that, for the first time, complex DNA and RNA
Abiogenesis
1346543
assemble thermodynamically into iron. Hoyle followed that in 1954 with a large paper describing how advanced fusion stages within massive stars would synthesize the elements from carbon to iron in mass. This is the first work of stellar nucleosynthesis. It and Hoyle's 1954 paper provided the roadmap to how the most abundant elements on Earth had been synthesized within stars from their initial hydrogen and helium, making clear how those abundant elements increased their galactic abundances as the galaxy aged. Hoyle's theory was expanded to other processes, beginning with the publication of a review paper in 1957 by Burbidge, Burbidge,
Stellar nucleosynthesis
965648
in trace amounts in earth's atmosphere. Silicate minerals are the most common type of mineral on earth. Silicon makes up 14.3 parts per million of the human body on average. Only the largest stars produce silicon via stellar fusion. Germanium makes up 2 parts per million of the earth's crust, making it the 52nd most abundant element there. On average, germanium makes up 1 part per million of soil. Germanium makes up 0.5 parts per trillion of seawater. Organogermanium compounds are also found in seawater. Germanium occurs in the human body at concentrations of 71.4 parts per billion. Germanium has
Carbon group
4100988
Micrometeorite A micrometeorite is essentially a micrometeoroid that has survived entry through Earth's atmosphere. The size of such a particle ranges from 50 µm to 2 mm. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs). Micrometeorites enter Earth's atmosphere at high velocities (at least 11 km/s) and undergo heating through atmospheric friction and compression. Micrometeorites individually weigh between 10 and 10 g and collectively comprise most of the extraterrestrial material
Micrometeorite
4207870
for I Zwicky 18's deficiency in heavy elements, indicating the galaxy's stars formed before these elements were abundant in the universe. The Cepheid distance also was validated through the observed brightness of the brightest red stars older than one billion years. The Hubble data suggest that I Zwicky 18 is 59 million light-years from Earth. The galaxy's larger-than-expected distance may explain why astronomers have had difficulty detecting older, fainter stars within the galaxy. The faint, old stars in I Zwicky 18 are almost at the limit of Hubble's resolution and sensitivity. I Zwicky 18 is classified as a dwarf irregular
I Zwicky 18
2073051
10,000 USD/kg, or about one-fourth that of gold. Lanthanum is much more common, being the second most abundant rare earth, and in addition to monazite can also be extracted economically from bastnäsite. The most available element in group 3 is yttrium, with annual production of 8,900 tonnes in 2010. Yttrium is mostly produced as oxide, by a single country, China (99%). Lutetium and scandium are also mostly obtained as oxides, and their annual production by 2001 was about 10 and 2 tonnes, respectively. Group 3 elements are mined only as a byproduct from the extraction of other elements. The metallic
Group 3 element
16026621
side of the periodic table and includes elements from the first two columns, the alkali metals (group 1) and alkaline earth metals (group 2), plus hydrogen and helium. Helium can be placed in the second group of s block as well as the 18th group of p-block, but most scientists consider it to rest at the top of group 18 i.e. above neon (atomic number 10) as it has many properties similar to the group 18 elements.General valance configration is ns1-2 Most s-block elements are highly reactive metals due to the ease with which their outer s-orbital electrons interact to
Block (periodic table)
1710822
production of heavier nuclei requires energy (is endothermic) instead of releasing it (exothermic). All these reactions have a very low rate at the temperatures and densities in stars and therefore do not contribute significantly to a star's energy production; with elements heavier than neon (atomic number > 10), they occur even less easily due to the increasing Coulomb barrier. Alpha process elements (or alpha elements) are so-called since their most abundant isotopes are integer multiples of four, the mass of the helium nucleus (the alpha particle). Stable alpha elements are: C, O, Ne, Mg, Si, S, Ar, Ca. They are
Alpha process
72612
element estimated to average 3 parts per million in the Earth's crust. It is the 45th most abundant element and the 36th among the metals. Nevertheless, it is more abundant than such elements as antimony, cadmium, tin, and tungsten, and two orders of magnitude more abundant than mercury and silver; it is 3.3% as abundant as rubidium, with which it is closely associated, chemically. Due to its large ionic radius, caesium is one of the "incompatible elements". During magma crystallization, caesium is concentrated in the liquid phase and crystallizes last. Therefore, the largest deposits of caesium are zone pegmatite ore
Caesium
233799
counted among the rare earth elements. The usual oxidation state is +3. Lanthanum has no biological role in humans but is essential to some bacteria. It is not particularly toxic to humans but does show some antimicrobial activity. Lanthanum usually occurs together with cerium and the other rare earth elements. Lanthanum was first found by the Swedish chemist Carl Gustav Mosander in 1839 as an impurity in cerium nitrate – hence the name "lanthanum", from the Ancient Greek "λανθάνειν" ("lanthanein"), meaning "to lie hidden". Although it is classified as a rare earth element, lanthanum is the 28th most abundant element
Lanthanum
14521498
nuclides in nature, which may form admixtures with the monoisotopics, and thus prevent them from being naturally mononuclidic. This happens in the cases of 7 () of the monoisotopic elements. These isotopes are monoisotopic, but due to the presence of the long lived radioactive primordial nuclide, are not mononuclidic. These elements are vanadium, rubidium, indium, lanthanum, europium, rhenium and lutetium. See the list below; in two noted cases (indium and rhenium), the long-lived radionuclide is actually the most abundant isotope in nature, and the stable isotope is less abundant. In 3 additional cases (bismuth, thorium, and protactinium), mononuclidic elements occur
Monoisotopic element
16271871
at night are often caused by activities by the sun 150 million kilometers away. The sun sends out a constant flow of charged particles known as solar wind. When these winds or eruptions are pointed or directed at the Earth, they can spark up sun-induced auroras. The greater the activity of the sun, the brighter the auroras we see. The colors of the aurora are determined by three elements which are: the density of the atmosphere, the composition of gases in the Earth's atmosphere, the altitude where aurora occurs and the level of energy involved. The most common color seen
Aurora Max
17554229
and it could be difficult navigating through the rings of Saturn. Also, Earth's atmosphere can be mined for carbon dioxide to produce fuel and to reduce the levels of greenhouse gas in the atmosphere. Hydrogen may fuel chemical and nuclear propulsion. Helium-3 may fuel nuclear propulsion. Methane may fuel chemical propulsion. Carbon dioxide mining on earth will reduce the level of greenhouse gases & can also produce fuel. Hydrogen and helium are abundant in outer planets. An aerostat would be a buoyant station in the atmosphere that gathers and stores gases. A vehicle would transfer the gases from the aerostat
Atmospheric mining
10510
dating. 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
Atom
7683558
most Earth-like of all the other planets in the Solar System. It is thought that Mars had a more Earth-like environment early in its history, with a thicker atmosphere and abundant water that was lost over the course of hundreds of millions of years. Given the foundations of similarity and proximity, Mars would make one of the most plausible terraforming targets in the Solar System. Side effects of terraforming include the potential displacement or destruction of indigenous life, even if microbial, if such life exists. The Martian environment presents several terraforming challenges to overcome and the extent of terraforming may
Terraforming of Mars
482491
Alkaline earth metal The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The elements have very similar properties: they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure. Structurally, they have in common an outer s- electron shell which is full; that is, this orbital contains its full complement of two electrons, which these elements readily lose to form cations with charge +2, and an oxidation state of +2. All the discovered alkaline earth metals occur
Alkaline earth metal
7898118
using less expensive, more Earth-abundant elements that are devoid of lead and tellurium (two materials that have been prevalent in the thermoelectric materials industry for the past couple decades). Tin selenides may be used for optoelectronic devices, solar cells, memory switching devices, and anodes for lithium-ion batteries. Tin(II) selenide has an additional use as a solid-state lubricant, due to the nature of its interlayer bonding. However, it is not the most stable of the chalcogenide solid-state lubricants, as tungsten diselenide has much weaker interplanar bonding, is highly chemically inert and has high stability in high-temperature, high-vacuum environments. Tin selenide Tin
Tin selenide
1957032
was its ability to form compounds with hydrogen. Under these conditions, the s- and f-block metals were strongly enriched during the formation of the Earth. The most enriched elements are rubidium, strontium and barium, which between them account for over 50 percent by mass of all elements heavier than iron in the Earth's crust. The nonmetallic lithophiles – phosphorus and the halogens – exist on Earth as ionic salts with s-block metals in pegmatites and seawater. With the exception of fluorine, whose hydride forms hydrogen bonds and is therefore of relatively low volatility, these elements have had their concentrations on
Goldschmidt classification
2364347
Geosphere There are several conflicting definitions for geosphere. The geosphere may be taken as the collective name for the lithosphere, the hydrosphere, the cryosphere, and the atmosphere. In Aristotelian physics, the term was applied to four spherical "natural places", concentrically nested around the center of the Earth, as described in the lectures "Physica" and "Meteorologica". They were believed to explain the motions of the four "terrestrial elements:" "Earth", "Water", "Air" and "Fire". In modern texts and in Earth system science, geosphere refers to the solid parts of the Earth; it is used along with atmosphere, hydrosphere, and biosphere to describe
Geosphere
5358930
not available or metal was scarce. A piece of the Cranbourne meteorite was made into a horseshoe around 1854. Today meteoritic iron is used in niche jewellery and knife production, but most of it is used for research, educational or collecting purposes. Meteoric iron also has an effect on the Earth's atmosphere. When meteorites descend through the atmosphere outer parts are ablated. Meteoric ablation is the source of many elements in the upper atmosphere. When meteoric iron is ablated it forms a free iron atom, that can react with ozone (O) to form FeO. This FeO may be the source
Meteoric iron
16955068
which resulted in high eustatic sea levels and created numerous shallow inland seas. In the Late Cretaceous, the climate was much warmer than present; however, throughout most of the period, a cooling trend is apparent. The tropics were much warmer in the early Cretaceous and became much cooler toward the end of the Cretaceous. 70 million years ago in the Late Cretaceous, the Earth was going through a greenhouse phase. There was abundant CO2 in the atmosphere which resulted in global warming. A theory was proposed that ocean circulation changed direction with two water masses in the Atlantic Ocean changing
Climate across Cretaceous–Paleogene boundary
197178
elements in Earth's crust, having an average mass fraction of 0.001 ppm in crustal rock; platinum is 10 times more abundant, gold is 40 times more abundant, and silver and mercury are 80 times more abundant. Tellurium is about as abundant as iridium. In contrast to its low abundance in crustal rock, iridium is relatively common in meteorites, with concentrations of 0.5 ppm or more. The overall concentration of iridium on Earth is thought to be much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the
Iridium
463531
of ytterbium range in atomic weight from 147.9674 atomic mass unit (u) for Yb to 180.9562 u for Yb. The primary decay mode of ytterbium isotopes lighter than the most abundant stable isotope, Yb, is electron capture, and the primary decay mode for those heavier than Yb is beta decay. The primary decay products of ytterbium isotopes lighter than Yb are thulium isotopes, and the primary decay products of ytterbium isotopes with heavier than Yb are lutetium isotopes. Ytterbium is found with other rare earth elements in several rare minerals. It is most often recovered commercially from monazite sand (0.03%
Ytterbium
4488342
the most primitive of all building techniques, molded mud, compressed as solidly as possible, and allowed to dry. This technique, used in Iran from ancient times, has never been completely abandoned. The abundance of heavy plastic earth, in conjunction with a tenacious lime mortar, also facilitated the development and use of brick. Iranian architecture makes use of abundant symbolic geometry, using pure forms such as circles and squares, and plans are based on often symmetrical layouts featuring rectangular courtyards and halls. Certain design elements of Persian architecture have persisted throughout the history of Iran. The most striking are a marked
Iranian architecture
397351
of methane deposits could have lowered it from a higher value, and counterbalance the effects of photosynthesis. The precise mechanism involved in the formation of cap carbonates is not clear, but the most cited explanation suggests that at the melting of a snowball Earth, water would dissolve the abundant from the atmosphere to form carbonic acid, which would fall as acid rain. This would weather exposed silicate and carbonate rock (including readily attacked glacial debris), releasing large amounts of calcium, which when washed into the ocean would form distinctively textured layers of carbonate sedimentary rock. Such an abiotic "cap carbonate"
Snowball Earth
482517
the next member of this series, calculations suggest that the next element of this series might actually be element 166. Alkaline earth metal The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The elements have very similar properties: they are all shiny, silvery-white, somewhat reactive metals at standard temperature and pressure. Structurally, they have in common an outer s- electron shell which is full; that is, this orbital contains its full complement of two electrons, which these elements readily
Alkaline earth metal
9406250
Extraterrestrial vortex Extraterrestrial cyclones are cyclones found on other planets or natural satellites other than the Earth. Venus has two large long-lived pairs of inverted anticyclones, one pair near each pole (polar vortices), discovered in 2006 by the Venus Express probe. Venus's southern pole vortex is the size of Europe and starts at the lower clouds of its atmosphere (42 kilometers from the surface) to the upper clouds of the atmosphere (63 kilometers from the surface). The vortex's elements are constantly being broken apart and coming back together as the vortex circles every 2.2 days. "The vortex is never destroyed,
Extraterrestrial vortex
4100999
fraction of particles entering the Martian atmosphere throughout the 60 to 1200-μm diameter range probably survive unmelted. Micrometeorite A micrometeorite is essentially a micrometeoroid that has survived entry through Earth's atmosphere. The size of such a particle ranges from 50 µm to 2 mm. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs). Micrometeorites enter Earth's atmosphere at high velocities (at least 11 km/s) and undergo heating through atmospheric friction and
Micrometeorite
3876006
atmosphere on average, though most of this condenses back onto the surface. Much of the sulfur dioxide in Io's atmosphere sustained by sunlight-driven sublimation of frozen on the surface. The day-side atmosphere is largely confined to within 40° of the equator, where the surface is warmest and most active volcanic plumes reside. A sublimation-driven atmosphere is also consistent with observations that Io's atmosphere is densest over the anti-Jupiter hemisphere, where frost is most abundant, and is densest when Io is closer to the Sun. However, some contributions from volcanic plumes are required as the highest observed densities have been seen
Io (moon)
406079
starting a decay chain named the thorium series that ends at stable Pb. In the universe, thorium and uranium are the only two radioactive elements that still occur naturally in large quantities as primordial elements. It is estimated to be over three times more abundant than uranium in the Earth's crust, and is chiefly refined from monazite sands as a by-product of extracting rare-earth metals. Thorium was discovered in 1829 by the Norwegian amateur mineralogist Morten Thrane Esmark and identified by the Swedish chemist Jöns Jacob Berzelius, who named it after Thor, the Norse god of thunder. Its first applications
Thorium
3126081
to thirteen waves, but some blades have up to 29. In contrast to the older straight type, most kris today have a wavy blade which is supposed to increase the severity of wounds inflicted upon a victim. According to traditional Javanese kejawen, kris contain all the intrinsic elements of nature: "tirta" (water), "bayu" (wind), "agni" (fire), "bantolo" (earth, but also interpreted as metal or wood which both come from the earth), and "aku" (lit: "I" or "me", meaning that the kris has a spirit or soul). All these elements are present during the forging of kris. Earth is metal forged
Kris
28508
more variable valence. They all have very large atomic and ionic radii and exhibit an unusually large range of physical properties. While actinium and the late actinides (from americium onwards) behave similarly to the lanthanides, the elements thorium, protactinium, and uranium are much more similar to transition metals in their chemistry, with neptunium and plutonium occupying an intermediate position. All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are the most abundant actinides on Earth. These are used in nuclear reactors and nuclear weapons. Uranium and thorium also have diverse
Actinide
28511
the lanthanides, the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups: transuranium elements, which follow uranium in the periodic table—and transplutonium elements, which follow plutonium. Compared to the lanthanides, which (except for promethium) are found in nature in appreciable quantities, most actinides are rare. The majority of them do not even occur in nature, and of those that do, only thorium and uranium do so in more than trace quantities. The most abundant or easily synthesized actinides are uranium and thorium, followed by plutonium, americium, actinium, protactinium, neptunium, and curium. The
Actinide
1870966
dome-shaped forms called diapirs when doing so. On Earth, salt domes are salt diapirs in the crust which rise through surrounding rock. Diapirs of molten low-density silicate rocks such as granite are abundant in the Earth's upper crust. The hydrated, low-density serpentinite formed by alteration of mantle material at subduction zones can also rise to the surface as diapirs. Other materials do likewise: a low-temperature, near-surface example is provided by mud volcanos. On the Moon, a distinctive basaltic material has been found that is high in "incompatible elements" such as potassium, rare earth elements, and phosphorus and is often referred
Planetary differentiation
165394
terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei. This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation. Previously, terrestrial helium—a non-renewable resource, because once released into the atmosphere it readily escapes into space—was thought to be in increasingly short supply. However, recent studies suggest that helium produced deep in the earth by
Helium
1533293
roles in all animals and some plants, making up bones and teeth, and used in some applications in cells, such as signals for cellular processeses. It is regarded as the most abundant mineral in the body's mass. Scandium (Sc) is the third element in period 4, between calcium and titanium, and is the first transition metal in the periodic table. Scandium is quite common in nature, but difficult to find because it is most prevalent in rare earth compounds, which are difficult to isolate elements from. Scandium has very few commercial applications because of the aforementioned facts, and currently its
Period 4 element
379372
the atmosphere of Sirius A relative to hydrogen is given by formula_1, meaning iron is 316% as abundant as in the Sun's atmosphere. The high surface content of metallic elements is unlikely to be true of the entire star; rather the iron-peak and heavy metals are radiatively levitated towards the surface. Sirius B is one of the more massive white dwarfs known. With a mass of it is almost double the average. This mass is packed into a volume roughly equal to the Earth's. The current surface temperature is 25,200 K. Because there is no internal heat source, Sirius B
Sirius
1621253
zero have on matter, such as with superconductivity. Helium is the second lightest element and is the second most abundant in the observable universe. Most helium was formed during the Big Bang, but new helium is being created as a result of the nuclear fusion of hydrogen in stars. On Earth, helium is relatively rare and is created by the natural decay of some radioactive elements because the alpha particles that are emitted consist of helium nuclei. This radiogenic helium is trapped with natural gas in concentrations of up to seven percent by volume, from which it is extracted commercially
Period 1 element
1621248
the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Elemental hydrogen is relatively rare on Earth, and is industrially produced from hydrocarbons such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets almost equally divided between fossil fuel upgrading, such as hydrocracking, and ammonia production, mostly for the fertilizer market. Hydrogen may be produced from water using the process of electrolysis, but this process is significantly more expensive commercially
Period 1 element
1639888
sublimated into polar-mesospheric noctilucent clouds. These are the highest clouds in the atmosphere and may be visible to the naked eye if sunlight reflects off them about an hour or two after sunset or a similar length of time before sunrise. They are most readily visible when the Sun is around 4 to 16 degrees below the horizon. Lightning-induced discharges known as transient luminous events (TLEs) occasionally form in the mesosphere above tropospheric thunderclouds. The mesosphere is also the layer where most meteors burn up upon atmospheric entrance. It is too high above Earth to be accessible to jet-powered aircraft
Atmosphere of Earth