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Cesium

Author: Robert Husted, Mollie Boorman

Atomic Number 55
Atomic Symbol Cs
CAS ID No. 7440-46-2
Atomic Weight 132.9050 amu
Electron Configuration [Xe] 6s1
Melting Point 28.6 C
Boiling Point 671 C
Density 1.870 g/cm3
History

(L. caesius: sky blue) Cesium was discovered spectroscopically in 1860 by Bunsen and Kirchhoff  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 elecytrolysis 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
Ref.: Wikimedia Commons, user Dnn87

The metal is characterized by a spectrum containing two bright lines in the blue along with several others in the red, yellow, and green wavelengths. 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 -116C. 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.

Isotopes

Cesium has more isotopes than any element--32--with masses ranging from 114 to 145.




Last Update: 2011-02-16