A metallic chemical element; symbol Sr. Atomic number 38; atomic weight 87.62; melting point 769°C; boiling point 1,384°C; specific gravity 2.6 at 20°C. Strontium is a soft, silver-yellow metal with three allotropic crystalline forms. It is found in nature only in the combined state, as in strontianite. It is used in fireworks, flares, and tracer bullets. The radioactive isotope Strontium-87, the daughter of Rubidium-87, has a half-life of 48.8 x 109 years.
The name derives from Strontian "a town in Scotland." The mineral strontianite is found in mines in Strontian. The element was discovered by the Scottish chemist and physician Thomas Charles Hope in 1792 observing the brilliant red flame color of strontium. It was first isolated by the English chemist Humphry Davy in 1808.