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| Atomic Number: | 36 | Atomic Symbol: | Kr | | Atomic Weight: | 83.80 | Electron Configuration: | 2-8-18-8 | | Shells: | 2,8,18,8 | Filling Orbital: | 4p6 | | Melting Point: | -157.2oC | Boiling Point: | -153.4oC | | Uses: | fluorescent lighting |
History(Gr. kryptos, hidden) Discovered in 1898 by Sir William Ramsay
and M.W. Travers of Britain, in the residue left after liquid air had nearly
boiled away.
SourcesKrypton 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.
Properties- It is one of the "noble" gases.
- It is characterized by its brilliant green and orange spectral lines.
- 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.
Uses- 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.
Compounds
Solid krypton is a white crystalline substance with a face-centered cubic
structure which is common to all the "rare gases."
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+.
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.
CostKrypton gas presently costs about $30/l.
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