Overview

Krypton was discovered in 1898 in London by William Ramsay and Morris Travers, who found it as a residue in liquefied air after the more volatile gases had boiled away. Its name comes from the Greek kryptos, hidden, marking how well it had escaped detection. Krypton is a colourless, odourless noble gas present in the atmosphere only in traces, and chemically almost wholly unreactive. Obtained in small amounts from liquefied air, krypton fills some high-performance light bulbs and fluorescent lamps, is used in certain lasers and in energy-efficient double glazing, and forms a few compounds with fluorine only with difficulty.

Krypton's supposed total inertness was revised in 1963, a year after Neil Bartlett's landmark synthesis of a xenon compound broke the noble gases' assumed unreactivity, when researchers produced krypton difluoride, a pale solid that remains one of the few well characterised krypton compounds. Krypton fluoride is also the active medium of an excimer laser widely used in advanced semiconductor photolithography, so an element first noticed only as a faint residue in liquefied air now plays a role in etching the very silicon chips that depend on far more abundant elements.