None

Xenon occurs in slight traces in gases within the Earth and is present to an extent of about 0.0000086 percent, or about one part in 10,000,000, by volume of dry air. Xenon is manufactured on a small scale by the fractional distillation of liquid air. The British chemists Sir William Ramsay and Morris W. Travers isolated the element (1898) by repeated fractional distillation of the noble gas krypton, which they had discovered six weeks previously.

The element xenon is used in lamps that produce intense, extremely short flashes of light, such as stroboscopes and lights for high-speed photography. When a charge of electricity is passed through the gas at low pressure, it emits a flash of bluish-white light; at higher pressures white light resembling daylight is emitted. Xenon flash lamps are used to activate ruby lasers.

Natural xenon is a mixture of nine stable isotopes in the following percentages; xenon-124 (0.096); xenon-126 (0.090); xenon-128 (1.92); xenon-129 (26.44); xenon-130 (4.08); xenon-131 (21.18); xenon-132 (26.89); xenon-134 (10.44); and xenon-136 (8.87). The xenon found in some stony meteorites shows a large proportion of xenon-129, believed to be a product of radioactive decay of iodine-129, whose half-life is 17,000,000 years. Study of the xenon-129 content of meteorites casts light on the history of the solar system. More than a dozen radioactive xenon isotopes produced by fission of uranium and other nuclear reactions are known. For example, xenon-135 (9.2-hour half-life) is produced by uranium fission in nuclear reactors, where it is troublesome because it absorbs fission-producing neutrons.

Noble gases were thought to be chemically inert until Neil Bartlett produced (1962) the first noble-gas compound, a red crystalline solid, xenon hexafluoroplatinate(V), that can best be
formulated as Xe(PtF6)x, in which x varies in value from one to two. Xenon was later observed to combine directly with fluorine to form a series of fluorides, XeF2, XeF4, and XeF6, of which
the tetrafluoride (XeF4) is the easiest to prepare. The oxides XeO3 and XeO4, made indirectly in aqueous solution, are explosively unstable when dry. Stable, insoluble xenate(VIII) salts, such as that of sodium, Na4XeO6 8H2O, and several other stable compounds--for example, the yellow solid cesium octafluoroxenate(VI), Cs2XeF8--have been prepared and studied.

Atomic number 54

Atomic weight 131.30

Melting point -111.9° C (-169.6° F)

Boiling point -107.1° C (-160.6° F)

Density (1 atm, 0 C) 5.887 g/litre

Valence 0, 2, 4, 6, 8

Electronic configuration 2-8-18-18-8 or (Kr)4d105s25p6

The mass numbers of the known isotopes of xenon range from 118 to 144; nine of these numbers correspond to stable isotopes. The xenon isotopes produced in the greatest amount
by nuclear fission are xenon-131, -132, -134, and -136, which are stable, and xenon-133, which is radioactive, having a half-life of about five days.

Xenon is the least volatile of the noble gases obtainable from the air. Its purification has been mentioned above (see Krypton). Numerous compounds of xenon have been prepared
since the discovery of the noble-gas compounds in 1962. Although xenon itself is an unusually safe anesthetic, its compounds appear to be toxic.