cesio

Cesio, or cesium (Cs), is a chemical element with atomic number 55. It belongs to the alkali metals in group 1. Cesium is among the softest metals and has a silvery-golden appearance. It has a very low melting point of 28.5°C and a boiling point of 671°C, making it a liquid near room temperature and highly reactive in ordinary conditions. Its density is about 1.93 g/cm³.

Cesium occurs only in trace amounts in the Earth’s crust and is mainly extracted from cesium-containing minerals such as pollucite. Commercial production involves mining, ore processing, and reduction or electrolysis to obtain metallic cesium. It is typically stored under mineral oil or in an inert atmosphere to prevent reaction with air or moisture.

Reactivity and compounds: Cesium is extremely reactive, especially with water, producing hydrogen gas and cesium hydroxide with heat. It readily forms a variety of salts, including cesium chloride, cesium carbonate, and cesium nitrate, and undergoes standard alkali-metal chemistry in solution and in solid compounds.

Isotopes: The only stable isotope is Cs-133. Numerous radioisotopes exist; the most widely known is Cs-137, produced by nuclear fission, with a half-life of about 30 years. Cs-137 is used in industrial radiography, calibration sources, and various irradiation applications, and has been used in medical and sterilization contexts, though it poses radiological hazards if not properly contained.

Applications: Cs-133’s hyperfine transition defines the second in atomic clocks, making cesium essential for high-precision timekeeping. In industry, cesium formate brine is used to increase density in oil-well drilling fluids, and cesium compounds are employed in glassmaking and specialty optics. Safety considerations include its high reactivity and radioactive isotopes, requiring careful handling, storage, and regulatory disposal.