Caesium is mined mostly from pollucite, while the radioisotopes, especially caesium-137, a fission product, are extracted from waste produced by nuclear reactors. It has only one stable isotope, caesium-133. It is the least electronegative element, with a value of 0.79 on the Pauling scale. The most reactive of all metals, it is pyrophoric and reacts with water even at −116 ☌ (−177 ☏). Caesium has physical and chemical properties similar to those of rubidium and potassium. It is a soft, silvery-gold alkali metal with a melting point of 28.5 ☌ (83.3 ☏), which makes it one of only five elemental metals that are liquid at or near room temperature. Although the element is only mildly toxic, the metal is a hazardous material and the radioisotopes present a significant health and ecological hazard in the environment.Ĭaesium or cesium is a chemical element with symbol Cs and atomic number 55. The radioactive isotope caesium-137 has a half-life of about 30 years and is used in medical applications, industrial gauges, and hydrology. Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids, but it has a range of applications in the production of electricity, in electronics, and in chemistry. Since then, caesium has been widely used in highly accurate atomic clocks. In 1967, acting on Einstein's proof that the speed of light is the most constant dimension in the universe, the International System of Units used two specific wave counts from an emission spectrum of caesium-133 to co-define the second and the metre. The first small-scale applications for caesium were as a "getter" in vacuum tubes and in photoelectric cells.
The German chemist Robert Bunsen and physicist Gustav Kirchhoff discovered caesium in 1860 by the newly developed method of flame spectroscopy. The most reactive of all metals, it is pyrophoric and reacts with water even at −116 ☌ (−177 ☏).
It is a soft, silvery-gold alkali metal with a melting point of 28.5 ☌ (83.3 ☏), which makes it one of only five elemental metals that are liquid at or near room temperature. All rights reserved.Caesium or cesium is a chemical element with symbol Cs and atomic number 55. Copyright © 2023, Columbia University Press. The Columbia Electronic Encyclopedia, 6th ed. It was first isolated by Carl Sefferburg in 1881 by electrolysis of its salts. Kirchoff discovered the element (the first to be discovered by the use of the spectroscope) and named it for the two bright blue lines characteristic of its spectrum. Minute quantities of cesium chloride are found in mineral springs and in seawater. Commercially useful quantities of inexpensive cesium are now available as a byproduct of the production of lithium metal. Cesium is found in the mineral pollux, or pollucite, which occurs on the island of Elba, in SW Africa, in the United States in Maine and South Dakota, and in Manitoba, Canada. Cesium-137, a waste product of nuclear reactors, is a radioactive isotope used in the treatment of cancer. Cesium compounds are used in the production of glass and ceramics and as antishock agents in conjunction with drugs containing arsenic. The chloride is used in photoelectric cells, in optical instruments, and in increasing the sensitivity of electron tubes. It also forms a sulfate, carbonate, nitrate, and cyanide. Cesium reacts with the halogens to form a fluoride, chloride, bromide, and iodide. It reacts with ice it reacts explosively with water to form cesium hydroxide, the strongest base known. Cesium reacts readily with oxygen it is sometimes used to remove traces of the gas from vacuum tubes and from light bulbs. Pure cesium can be prepared by electrolysis of fused cesium cyanide in an inert atmosphere the pure metal must be kept under an inert liquid or gas or in a vacuum to protect it from air and water. It is the most reactive metal and is never found uncombined in nature.
Chemically cesium resembles rubidium and potassium. Cesium liquefies in a warm room mercury and gallium are the only other metals with this property. An alkali metal, it is the most alkaline of all elements. Cesium is a ductile, soft-as-wax, silver-white metallic element. Cesium sē´zēəm, a metallic chemical element symbol Cs at.
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