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Atomic Number: 55
Atomic Symbol: Cs
Atomic Weight: 132.9054
Electron Configuration: [Xe]6s1
History
(L. caesius, sky blue) Cesium was discovered spectroscopically by
Bunsen and Kirchhoff in 1860 in mineral water from Durkheim.
Sources
Cesium, an alkali metal, occurs in lepidolite, pollucte (a hydrated
silicate of aluminum and cesium), and in other sources. One of the world's
richest sources of cesium is located at Bernic Lake, Manitoba. The deposits are
estimated to contain 300,000 tons of pollucite, averaging 20% cesium.
It can be isolated by electrolysis of the fused cyanide and by a
number of other methods. Very pure, gas-free cesium can be prepared by thermal
decomposition of cesium azide.
Properties
The metal is characterized by a spectrum containing two bright lines
in the blue along with several others in the red, yellow, and green. It is
silvery white, soft, and ductile. It is the most electropositive and most
alkaline element.
Cesium, gallium, and
mercury are the only three metals that are liquid
at room temperature. Cesium reacts explosively with cold water, and reacts with
ice at temperatures above -116° C. Cesium
hydroxide, the strongest base known, attacks glass.
Uses
Because of it has great affinity for oxygen, the metal is used as a
"getter" in electron tubes. It is also used in photoelectric cells, as well as a
catalyst in the hydrogenation of certain organic compounds.
The metal has recently found application in ion propulsion
systems. Cesium is used in atomic clocks, which are accurate to 5 s in 300
years. Its chief compounds are the chloride and the nitrate.
Isotope
Cesium has more isotopes than any element--32--with masses ranging
from 114 to 145.
Sources: CRC Handbook of Chemistry and
Physics and the American Chemical Society.
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