Strontium

Strontium is a chemical element with the symbol Sr and atomic number 38. It belongs to the alkaline earth metals group, positioned between calcium and barium. It is a soft, silvery metal that reacts quickly with air and water.

Because of its high reactivity, it does not occur naturally in pure form; instead it is found in minerals, particularly celestine (strontium sulfate) and strontianite (strontium carbonate). The name derives from the village of Strontian in Scotland, where the mineral was discovered in the late 18th century.

Chemical and physical properties

Strontium typically forms the Sr²⁺ ion, releasing two electrons. Its chemistry closely resembles that of calcium, which causes the human body to substitute strontium for calcium, particularly in bones. When burned, its flames produce a red color, used in fireworks and emergency signals.

Isotopes

Strontium has stable naturally occurring isotopes. The most notable radioactive isotope is strontium-90, a product of nuclear fission. Because it accumulates in bones, it is considered a health hazard when released into the environment following nuclear accidents or weapons testing. Another isotope, strontium-89, is used medically to treat bone pain associated with cancer.

Applications

For a long period, strontium was used in cathode ray tube television screens to suppress X-ray radiation. When that technology was replaced, demand fell. Today it is used in pyrotechnic colorants, ferrite magnets, and certain dental materials for sensitivity relief. Strontium compounds are also added to treatments that strengthen tooth enamel.