John Dalton's original atomic hypothesis assumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed that water's formula was HO, giving the atomic mass of oxygen as 8 times that of hydrogen, instead of the modern value of about 16. In 1805, Joseph Louis Gay-Lussac and Alexander von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen; and by 1811 Amedeo Avogadro had arrived at the correct interpretation of water's composition, based on what is now called Avogadro's law and the assumption of diatomic elemental molecules.[a]
What did John Dalton think that all elements were in number present in compounds? What did Dalton think the atomic ratios were between atoms in compounds? What was Dalton's erroneous formula for water? What element did Gay-Lussac and von Humboldt discover was present in twice the amount of oxygen in water? What theory was arrived at in 1811 that presented the assumption of diatomic molecules?