Krypton

William Ramsay and Morris Travers discovered krypton in 1898. They discovered it in the residue remaining after liquid air had been fractionally distilled. With the oxygen and nitrogen gone, a bright yellow spectral line that was neither sodium nor helium revealed the presence of a new element. The element name comes from the Greek word 'kryptos', meaning hidden.

Krypton is considered to be non-toxic.

Krypton is a colorless, odorless, inert gas.

Although it is extremely unreactive krypton can react with fluorine, and a few compounds of the element have been prepared, including krypton (II) fluoride and krypton clathrates.

Solid krypton is white and crystalline.

Krypton is used in lighting products. Ionized krypton gas appears whitish - see photo on left - which makes krypton-based bulbs useful as a brilliant white light source in high speed photography. An important lighting use is also in high-powered, flashing airport runway lights.

Krypton is employed alongside other gases to make luminous 'neon light' style signs that glow with a greenish-yellow light.

It is used as a filling gas for energy saving fluorescent lights and as an inert filling gas in incandescent bulbs.

Between 1960 and 1980, an international agreement defined the meter length in terms of the wavelength of light emitted from the krypton isotope, ⁸⁶Kr. (The meter is now defined as the distance traveled by light in vacuum during a time of 1/299,792,458 of a second. The time is measured using a cesium atomic clock.)

Krypton is obtained commercially by fractional distillation of liquid air.

Krypton has 25 isotopes whose half-lives are known, with mass numbers 71 to 95. Of these, six are stable: ⁷⁸Kr, ⁸⁰Kr, ⁸²Kr, ⁸³Kr, ⁸⁴Kr and ⁸⁶Kr. The most abundant isotope is ⁸⁴Kr at 57.03%.