strontium

Strontium is a soft, silvery-white metallic element with the chemical symbol Sr and atomic number 38. It belongs to the alkaline earth metals in group 2 of the periodic table. In its compounds, strontium commonly exhibits the +2 oxidation state. The metal is reactive, especially with water and air, and forms oxides and hydroxides such as SrO and Sr(OH)2. Strontium has a density of about 2.64 g/cm3 and a melting point of 777°C, with a boiling point near 1382°C.

Strontium occurs in the Earth's crust mainly in the minerals celestite (SrSO4) and strontianite (SrCO3). It is usually obtained as a byproduct of mining for other metals and is produced commercially by reducing strontium oxide or by electrochemical methods. Naturally occurring isotopes include 84Sr, 86Sr, 87Sr, and 88Sr; the radiogenic 87Sr from the decay of 87Rb is used in geochronology. A radioactive isotope, 90Sr, is produced by nuclear fission and has seen use in medical and industrial radiation sources.

Applications of strontium include colorants and additives for glass and ceramics, producing a bright red color in fireworks, and the use of strontium ferrite (SrFe12O19) in permanent magnets. Strontium compounds are also studied for potential medical uses, although high doses can be hazardous. Strontium is not known to be essential for humans.

Historically, strontium was discovered in 1790 by Adair Crawford and William Cruickshank in a mineral from Strontian, Scotland, and was isolated as an element by Humphry Davy in 1808. The name honors the locality from which the first ore was described.