Noble gas
The noble gases are the elements in group 8A of the periodic table (group 18 in the numbering recommended by IUPAC): helium, neon, argon, krypton, xenon and radon.[1][2][2] They are the least reactive elements in the periodic table.[2] The group is also called the rare gases or inert gases, though none of these names fits perfectly; they are "rare" only compared with oxygen and nitrogen.[3]
Properties
The noble gases are all gases at room temperature, and they exist as single, separate atoms rather than as molecules.[2] Their boiling points are very low because the forces between their atoms are very weak.[3] They are unreactive and do not form ions.[4] Scientists later explained this using the electron theory of the atom: the noble gases have completed shells of electrons. Other elements tend to combine in ways that give them the same electron arrangement as a noble gas.[5]
Occurrence
Argon makes up about 0.9 per cent of the atmosphere by volume, and most noble gases are produced by separating liquid air. Helium is found in natural gas from oilfields and in rocks, where it forms from alpha particles. Radon is radioactive and is found in minerals containing uranium and thorium.[3]
Discovery
Argon
In 1888 Lord Rayleigh set out to measure the densities of oxygen and nitrogen accurately. He found that nitrogen taken from the air was slightly heavier than nitrogen made from chemicals, and in 1892 he wrote to the journal Nature asking for suggestions.[5][5] The chemist William Ramsay replied that he too was puzzled.[5] In 1893 Ramsay began removing nitrogen from air by heating magnesium in it, to see what was left.[5]
The two men found a gas whose spectrum showed red and green lines that belonged to no known gas. Ramsay could not make it combine with other substances, so it was named argon, from the Greek for "idle".[5] Their work was announced in 1894 and read to the Royal Society in January 1895.[5][5] Argon was found to be made of single atoms with an atomic weight of 40.[5]
Helium and the others
Helium had been seen in the spectrum of the Sun by Lockyer in 1868.[6] In 1895 Ramsay found it on Earth, in a mineral called cleveite.[5] By 1898 Ramsay and Morris Travers had identified neon, krypton and xenon, all of which were chemically inert. In 1903 Soddy identified radon as a gas given off by radium.[5] Only in 1900, after neon, krypton and xenon had been found, did doubtful chemists accept a whole new group with a valency of zero.[5] One history of chemistry describes how the discovery of the rare gases "proved more important than any prior discoveries of new elements".[7]
Noble gas compounds
For many years chemists believed that the noble gases could not form compounds. Until 1962, all attempts to make them do so had failed.[3] That year, Neil Bartlett made a compound of xenon using platinum hexafluoride, after noticing that xenon and oxygen need almost the same energy to remove an electron. Xenon tetrafluoride (XeF4) soon followed.[5][8]
See also
References
- ↑ Young, Susan M.; Vining, William J.; Day, Roberta; Botch, Beatrice (2018). General Chemistry: Atoms First. Boston: Cengage Learning. pp. 49–50. ISBN 978-1-337-61229-6.
{{cite book}}:|access-date=requires|url=(help) - ↑ 2.0 2.1 2.2 2.3 Young, Susan M.; Vining, William J.; Day, Roberta; Botch, Beatrice (2018). General Chemistry: Atoms First. Boston: Cengage Learning. p. 50. ISBN 978-1-337-61229-6.
{{cite book}}:|access-date=requires|url=(help) - ↑ 3.0 3.1 3.2 3.3 Mackay, K. M.; Mackay, R. A.; Henderson, W. (2002). Introduction to Modern Inorganic Chemistry (6th ed.). Cheltenham: Nelson Thornes. section 17.9: The helium Group. ISBN 0-7487-6420-8. Retrieved 2026-10-23.
- ↑ Young, Susan M.; Vining, William J.; Day, Roberta; Botch, Beatrice (2018). General Chemistry: Atoms First. Boston: Cengage Learning. pp. 110–111. ISBN 978-1-337-61229-6.
{{cite book}}:|access-date=requires|url=(help) - ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 Brock, William H. (1992). The Fontana History of Chemistry (ePub ed.). London: Fontana Press. Chapter 9: Principles of Chemistry, section The Inert Gases. ISBN 9780007394968.
{{cite book}}:|access-date=requires|url=(help) - ↑ Brock, William H. (1992). The Fontana History of Chemistry (ePub ed.). London: Fontana Press. Chapter 9: Principles of Chemistry, section The Rare Earths / just before The Inert Gases. ISBN 9780007394968.
{{cite book}}:|access-date=requires|url=(help) - ↑ Brock, William H. (1992). The Fontana History of Chemistry (ePub ed.). London: Fontana Press. Chapter 9: Principles of Chemistry, section Conclusion. ISBN 9780007394968.
{{cite book}}:|access-date=requires|url=(help) - ↑ Mackay, K. M.; Mackay, R. A.; Henderson, W. (2002). Introduction to Modern Inorganic Chemistry (6th ed.). Cheltenham: Nelson Thornes. section 17.9.1: Xenon compounds. ISBN 0-7487-6420-8. Retrieved 2026-10-23.