Cesium

Element Cesium

Cesium (Caesium) is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F). Cesium is used in various industries, from the oil industry as cesium formate in drilling fluid, atomic clocks, centrifugation fluids, and cesium vapor thermionic generators, which convert heat energy to electrical energy.
Cesium is a naturally occurring element found combined with other elements in rocks, soil, and dust in low amounts. Naturally occurring cesium is not radioactive and is referred to as stable cesium.
Cesium, the most electropositive and least abundant of the five naturally occurring alkali metals, was discovered spectroscopically in 1860. The first cesium metal was produced in 1881. Because cesium is not mined domestically, the United States is completely dependent on imports. Historically, the most important use for cesium has been in research and development, primarily in chemical and electrical applications.

Caesium (55Cs) has 40 known isotopes, making it, along with barium and mercury, one of the elements with the most isotopes.[3] The atomic masses of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable. The longest-lived radioisotopes are 135Cs with a half-life of 2.3 million years, 137Cs with a half-life of 30.1671 years and 134Cs with a half-life of 2.0652 years. All other isotopes have half-lives less than 2 weeks, most under an hour.