Strontium

Name:Strontium
Symbol:Sr
Atomic Number:38
Atomic Mass:87.62
Density: 33.94 g/cm^3
Melting Point:777 °C
Boiling Point:1382 °C
Group Number:2
Group Name:Alkaline Earth Metals
Standard State:Solid at room temperature
Color:silvery white
Classification:Metallic
Strontium does not occur as the free element. Strontium is softer than calcium and decomposes water more vigorously. Freshly cut strontium has a silvery appearance, but rapidly turns a yellowish color with the formation of the oxide. The finely divided metal ignites spontaneously in air. Volatile strontium salts impart an excellent crimson color to flames, and these salts are used in pyrotechnics.

The picture above shows the color arising from adding strontium sulphate salt (SrSO₄) to a burning mixture of potassium chlorate and sucrose. Do not attempt this reaction unless are a professionally qualified chemist and you have carried out a legally satisfactory hazard assessment.

Strontium-90 (⁹⁰Sr) has a half-life of 28 years. It is a product of nuclear fallout and presents a major health problem. Strontium titanate is an interesting optical material as it has an extremely high refractive index and an optical dispersion greater than that of diamond. It has been used as a gemstone, but it is very soft.

Isolation

Strontium metal is available commercially and there is no need to make it in the laboratory. Commercially it is made on small scale by the electrolysis of molten strontium chloride, SrCl₂.

cathode: Sr²⁺(l) + 2e^- → Sr anode: Cl^-(l) → ¹/₂Cl₂ (g) + e^-

Strontium metal can also be isolated from the reduction of strontium oxide, SrO, with aluminum.

6SrO + 2Al → 3Sr + Sr₃Al₂O₆