Strontium ( /ˈstrɒntiəm/ STRON-tee-əm) is a chemical element with symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite. While natural strontium is stable, the synthetic 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.
Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered in 1790 by Adair Crawford and William Cruickshank. The production of sugar from sugar beet was in the 19th century the largest application. Strontium compounds are today mostly used for the production of cathode ray tubes. The displacement of cathode ray tubes by other display methods in television sets is changing the overall consumption.