krypton (Kr)

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 discovered by William Ramsey and M. W. Travers in London in1898; its name comes from the Greek kryptos, meaning "hidden." Krypton (Kr) is a member of the noble 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. The isotope ⁸⁶Kr has a spectral line used as the standard measure of length. One meter is defined as 1,650,763.73 wavelengths of this line.

Krypton-81 in medicine

Krypton-81m, the shortest-lived isotope of krypton (half-life 13 seconds), and the shortest-lived isotope used in medicine, can be used to investigation the ventilation of the lungs. The patient breathes a small quantity of the gas, the arrival of which in different parts of the lungs is recorded by a gamma camera. This test is often performed as part of ventilation-perfusion scanning to look for pulmonary emboli.

Chemistry of krypton

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.

atomic number	36
relative atomic mass	83.80
electron configuration	1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶
melting point	-156.6°C (-249.9°F)
boiling point	-152.3°C (-242.1°F)
density	3.73 kg/m³ (0 °C)

Related category

• INORGANIC CHEMISTRY

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