Krypton in a discharge tube displays its green and orange spectral signature. Gaseous krypton is colorless, while solid krypton is white. Credit: Pslawinski, Wikipedia
A colorless, odorless, highly unreactive gaseous element. Krypton (Kr) is a member of the inert gas family (abundance 1.1 × 10-3%). It is obtained pure by fractional distillation of air. Krypton is used chiefly (with argon) in gas-discharge lamps, fluorescent lights, and electronic flash tubes.
Krypton forms a limited range of chemical compounds and some clathrates. It combines with fluorine in an electric discharge to give krypton (II) fluoride (KrF2), a highly reactive, odorless crystalline solid, which decomposes slowly at 20°C, is hydrolyzed by water, and forms adducts with Lewis acid fluorides, e.g. KrF2·2SbF5. KrF2 is used as a strong fluorinating agent.