Properties and Overview of Strontium

Overview:

Strontium (Sr) is a chemical element with the symbol Sr and atomic number 38, belonging to the alkaline earth metal group in the periodic table, which also includes beryllium, magnesium, calcium, barium, and radium. Strontium was discovered in 1790 by Scottish chemist Adair Crawford while studying a mineral sample from a lead mine in Strontian, Scotland, from which the element takes its name. The metal was first isolated in 1808 by Sir Humphry Davy using electrolysis. Physically, strontium is a soft, silvery metal that is somewhat malleable and ductile. It is relatively reactive, particularly when exposed to air, forming a yellowish oxide layer that tarnishes its surface. Strontium has a density of about 2.64g/cm³, a melting point of 777°C, and a boiling point of 1,375°C. Due to its position in the periodic table, strontium shares several physical characteristics with calcium and barium, such as similar densities and reactivities.
Chemically, strontium strongly tends to form ionic compounds, usually in the +2 oxidation state, as Sr²⁺ ions. This reactivity is characteristic of alkaline earth metals, which quickly lose their two outermost electrons. Strontium reacts vigorously with water, producing strontium hydroxide (Sr(OH)₂) and hydrogen gas. It also reacts with oxygen to form strontium oxide (SrO) and with halogens to produce strontium halides, such as strontium chloride (SrCl₂). One of the most well-known compounds of strontium is strontium carbonate (SrCO₃), which is used in fireworks and flares to create a bright red flame due to the element's ability to emit a distinctive red color when burned.
Regarding safety, strontium poses minimal risks in its natural, stable forms. However, one of its radioactive isotopes, strontium-90, is a byproduct of nuclear reactions and poses significant health risks. Strontium-90 can replace calcium in bones due to its chemical similarity, leading to radiation exposure from within the body, which can increase the risk of bone cancer and leukemia. Therefore, handling radioactive strontium requires stringent safety protocols to prevent contamination and exposure. Non-radioactive strontium compounds, such as those used in medical treatments and consumer products, are generally considered safe when used appropriately. In medical applications, strontium ranelate treats osteoporosis, leveraging strontium's ability to mimic calcium and promote bone formation.

Production:

Strontium is typically produced by reducing strontium oxide with aluminum at high temperatures, yielding metallic strontium. The metal is then purified by distillation or electrolysis of molten strontium chloride. Naturally, strontium occurs primarily in the minerals celestite (strontium sulfate, SrSO₄) and strontianite (strontium carbonate, SrCO₃), from which it is commercially extracted. The extraction process involves converting the mineral into strontium carbonate, which can then be further processed into other compounds or reduced to produce metallic strontium.

Applications:

Strontium has several critical industrial and commercial applications. One of the most recognizable uses is producing fireworks and pyrotechnics, where strontium compounds produce red flames, especially strontium carbonate and strontium nitrate. Strontium is also used to manufacture glass for color television cathode ray tubes (CRTs), which help block X-ray emissions. Although modern display technologies have replaced mainly CRTs, this application was historically significant. Additionally, strontium is used in producing ferrite magnets, which are used in small motors and electronic devices. Strontium compounds are also used in refining zinc, producing ceramics, and medical applications such as bone health supplements.

Summary:

Strontium is an alkaline earth metal with distinct physical and chemical properties, including its reactivity with water and air and its tendency to form compounds in the +2 oxidation state. It is produced primarily from celestite and strontianite minerals and has applications ranging from pyrotechnics to medical treatments. While stable strontium compounds are generally safe, the radioactive isotope strontium-90 poses significant health risks and requires careful handling. Strontium's unique properties continue to make it valuable in industrial and medical fields.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for strontium below: