Krypton - Kr General Information Discovery Krypton was discovered by Sir William Ramsay and M.W. Travers in 1898 in London, in the residue remaining after nitrogen and oxygen had boiled away from liquid air. Appearance Krypton is a colourless, odourless gas. Source Krypton is obtained by distillation from liquid air. Uses Krypton is used commercially as a low-pressure filling gas for fluorescent lights. It is also used in certain photographic flash lamps for high-speed photography. Radioactive krypton was used to estimate Soviet nuclear production. The gas is a product of all nuclear reactors, so the Russian share was found by subtracting the amount that comes from Western reactors from the total in the air. Biological Role Krypton has no known biological role. General Information The spectral lines of krypton - brilliant green and orange - are easily produced and very sharp. The orange-red line of 86Kr is used as the fundamental unit of length: 1 metre=1650763.73 wavelengths. Some krypton compounds can be made, including krypton(II) fluoride, and some clathrates.

	Physical Information
	Atomic Number		36
	Relative Atomic Mass (12C=12.000)		83.8
	Melting Point/K		117
	Boiling Point/K		121
	Density/kg m-3		3.75 (gas, 273K)
	Ground State Electron Configuration		[Ar]3d104s24p6
	Electron Affinity(M-M-)/kJ mol-1		+39

	Key Isotopes
	nuclide	78Kr	80Kr	82Kr	83Kr	84Kr
	atomic mass	77.92	79.92	81.91	82.91	83.91
	natural abundance	0.35%	2.25%	11.6%	11.5%	57.0%
	half-life	stable	stable	stable	stable	stable
	nuclide	85Kr	86Kr
	atomic mass	84.91	85.91
	natural abundance	0%	17.3%
	half-life	10.76 yrs	stable

Other Information
Enthalpy of Fusion/kJ mol-1		1.64
Enthalpy of Vaporisation/kJ mol-1		9.05
Oxidation States
Kr0, Kr+2

	Ionisation Energies/kJ mol-1
	M - M+	1350.7
	M+ - M2+	2350
	M2+ - M3+	3565
	M3+ - M4+	5070
	M4+ - M5+	6240
	M5+ - M6+	7570
	M6+ - M7+	10710
	M7+ - M8+	12200
	M8+ - M9+	22229
	M9+ - M10+	28900