|
|
Atomic Number: |
55 |
Melting Point: | 28.5 ºC | |
| Atomic Symbol: | Cs | Boiling Point: | 671 ºC | ||
| Atomic Weight: | 132.9054 amu | Density: | 1879
kg/m 3 |
||
| Atomic Radius: |
265.4 pm |
Oxidation States: | 1 | ||
| Covalent Radius: | 225 pm | Electron Configuration: | [Xe]6s1 | ||
| van der Waals Radius: |
-- |
State of Matter: | solid |
(L. caesius: sky blue) Cesium was discovered spectroscopically in 1860 by Bunsen and Kirchhoff in mineral water from Durkheim.
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.
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.
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. Historically, the most important use for cesium has been in research and development, primarily in chemical and electrical applications.
Cesium has more isotopes than any element, 32, with masses ranging from 114 to 145.
Cs-134 has been used in hydrology as a measure of cesium output by the nuclear power industry. This isotope is used because, while it is less prevalent than either Cs-133 or Cs-137, Cs-134 can be produced solely by nuclear reactions. Cs-135 has also been used in this function.
Cesium is highly explosive in cold water. Cesium should be considered highly toxic and should be handled with great care. Some of its radioisotopes are even more toxic. Cesium hydroxide is an extremely strong base, and can attack glass.
It is extremely corrosive to tissue. Ingestion will cause burns and perforations of the gastrointestinal tract. Severe thermal burns, corrosion and ulceration of the skin and eye may occur upon direct contact. If cesium ignites, it will cause thermal burns. The metal rapidly forms caustic and highly corrosive alkali hydroxide with evolution of heat. Severe thermal and chemical burns will result at every point of human contact.
Cesium compounds may cause hyper-irritability, including spasms, dizziness, abdominal cramps, vomiting, diarrhea, convulsions and collapse. Chronic ingestion of cesium has been fatal to laboratory animals, possibly due to the replacement of potassium. Chronic exposure also can have blood and neuromuscular effects.
