cesiumatomen

Cesium atoms (symbol Cs, atomic number 55) are the alkali metal cesium. They are soft, silvery-gold solids with a melting point of 28.5°C, and they are highly reactive, oxidizing in air and reacting vigorously with water to yield cesium hydroxide and hydrogen gas.

Natural occurrence and production: The only stable isotope is Cs-133. Cesium occurs in trace amounts in minerals such as pollucite and is mined from cesium-bearing pegmatites. Industrially, elemental cesium is produced by purification of cesium salts and reduction or electrolysis to yield metal, typically stored under oil or in an inert atmosphere to prevent oxidation.

Chemistry: As a Group 1 element, cesium forms compounds in the +1 oxidation state. Its oxides (Cs2O), hydroxides (CsOH), hydrides (CsH), and salts such as CsCl and Cs2CO3 are known. Cesium has a low ionization energy and a large ionic radius, contributing to its high reactivity with air and water.

Applications and isotopes: The stable Cs-133 isotope is used in atomic clocks; its hyperfine transition defines the second and underpins national time standards and GPS. Radioisotopes such as Cs-137 are produced by nuclear fission and have uses in medicine and industry, while presenting radiological hazards.

Safety and handling: Because of its reactivity, elemental cesium is handled with care and stored under oil or in an inert atmosphere. Contact with water or moisture can generate heat and hydrogen gas, with potential for ignition.

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