Two papers on "Experiments with Airs," printed in 1784 and 1785, contain the great discoveries of the compound nature of water and the composition of nitric acid of English chemist Henry Cavendish (1731-1810). The presence of unknown material (actually the Noble Gases) was noted by Cavendish. He carried an experiment whether the whole of a given portion of nitrogen could be reduced to nitric acid (by combination with magnesium) and oxygen. Starting with a chamber containing air from which he was able to remove nitrogen he found that a small fraction, resisted the change - the residual content of the chamber - and in fact, mostly argon together with other trace elements in air.

In his book The Gases of the Atmosphere (1896), William Ramsay (1852-1916) repeated a suspicion he had stated in 1892 that there was an eighth group of new elements at the end of the periodic table. Noting that the element had a valence of zero, he postulated that a new group existed in the periodic table, and began the search for its new members. Using spectroscopy, he was able to determine that lines of a gas corresponded to lines found in the Sun and attributed to a new element called helium. Further experimentation in 1898 yielded three as yet unknown fractions in air: neon, krypton , and xenon. Ramsay was awarded the Nobel Prize for Chemistry in 1904 for his discovery of inert gases in air and their locations in the periodic table. He was made a KCB in 1902.

Elements of the Periodic Table
Elementsort icon Atomic numbersort icon Atomic weightsort icon Boiling pointsort icon Densitysort icon Heat fusionsort icon Heat vapoursort icon Melting pointsort icon Specific heat capacitysort icon Thermal conductivitysort icon
Argon 18 39.95 87.36° K 1400 kg/m³ 1.18 kJ/mol 6.53 kJ/mol 83.76° K
Helium 2 4 4.26° K 126 kg/m³ 0.02 kJ/mol 0.08 kJ/mol 3.46° K
Krypton 36 83.8 121.16° K 2600 kg/m³ 1.63 kJ/mol 9.05 kJ/mol 115.86° K
Neon 10 20.18 27.16° K 1200 kg/m³ 0.34 kJ/mol 1.77 kJ/mol 24.56° K
Radon 86 86
Xenon 54 131.3 165.16° K 3060 kg/m³ 2.3 kJ/mol 12.65 kJ/mol 161.26° K
Amazon Books
Image of Mendeleev on the Periodic Law: Selected Writings, 1869-1905
Author: Dmitri Ivanovich Mendeleev
Publisher: Dover Publications Inc. (2005)
Binding: Paperback, 320 pages