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Atomic Number: 36
Atomic Symbol: Kr
Atomic Weight: 83.80
Electron Configuration: [Ar]4s23d104p6
History
(Gr. kryptos, hidden) Discovered in 1898 by Ramsay and Travers in the
residue left after liquid air had nearly boiled away. In 1960 it was
internationally agreed that the fundamental unit of length, the meter, should be
defined in terms of the orange-red spectral line of 86Kr. This
replaced the standard meter of Paris, which was defined in terms of a bar made
of a platinum-iridium alloy. In October 1983 the meter, which originally was
defined as being one ten millionth of a quadrant of the earth's polar
circumference, was again redefined by the International Bureau of Weights and
Measures as being the length of a path traveled by light in a vacuum during a
time interval of 1/299,792,458 of a second.
Sources
Krypton is present in the air to the extent of about 1 ppm. The
atmosphere of Mars has been found to contain 0.3 ppm of krypton. Solid krypton
is a white crystalline substance with a face-centered cubic structure which is
common to all the "rare gases."
Properties
It is one of the "noble" gases. It is characterized by its brilliant
green and orange spectral lines.
Isotopes
Naturally occurring krypton contains six stable isotopes. Seventeen
other unstable isotopes are now recognized. The spectral lines of krypton are
easily produced and some are very sharp. While krypton is generally thought of
as a rare gas that normally does not combine with other elements to form
compounds, it now appears that the existence of some krypton compounds is
established. Krypton difluoride has been prepared in gram quantities and can be
made by several methods. A higher fluoride of krypton and a salt of an oxyacid
of krypton also have been reported. Molecule-ions of ArKr+ and KrH+
have been identified and investigated, and evidence is provided for the
formation of KrXe or KrXe+.
Uses
Krypton clathrates have been prepared with hydroquinone and
phenol. 85Kr has found recent application in chemical analysis. By
imbedding the isotope in various solids, kryptonates are formed. The activity of
these kryptonates is sensitive to chemical reactions at the surface. Estimates
of the concentration of reactants are therefore made possible. Krypton is used
in certain photographic flash lamps for high-speed photography. Uses thus far
have been limited because of its high cost.
Sources: CRC Handbook of Chemistry and
Physics and the American Chemical Society.
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