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Facts About Strontium

Strontium
Electron configuration and elemental properties of strontium.
Credit: Greg Robson/Creative Commons, Andrei Marincas | Shutterstock
Atomic Number: 38
Atomic Symbol: Sr
Atomic Weight: 87.62
Melting Point: 1,431 F (777 C)
Boiling Point: 2,520 F (1,382 C)

Word origin: Strontium is named for Strontian, a town in Scotland.

Discovery: In 1790, Adair Crawford recognized a new mineral (strontianite) as different from other barium minerals. Strontium was not isolated, however, until 1808 when Humphry Davey isolated it through electrolysis.

Properties of strontium

Strontium is an alkaline earth metal similar to calcium and barium. Freshly cut strontium has a silvery appearance but it rapidly turns yellowish with the formation of oxide. If finely divided, it ignites spontaneously in the air. Its volatile salts can lend a beautiful crimson color to flames. [See Periodic Table of the Elements]

Strontium is softer than calcium and decomposes in water more vigorously. It does not absorb nitrogen below 380 C (716 F). It should be kept under kerosene to prevent oxidation. Three allotropic forms of the metal exist, with transition points at 235 and 540 C (455 and 1,004 F).

Strontium
A crystal of celestite, a primary source of strontium.
Credit: Greg Robson/Creative Commons, Andrei Marincas | Shutterstock

Sources of strontium

Strontium is found primarily as celestite, also called celestine, and strontianite. The metal can be prepared by electrolysis of the fused chloride mixed with potassium chloride. It can also be made by reducing strontium oxide with aluminum in a vacuum at a temperature at which strontium distills off.

Uses of strontium

Strontium has many important uses. Its isotope Strontium-82 is used for cardiac imaging via Positron Emission Tomography (PET) at hospitals across the country. It is also used in producing ferrite magnets and refining zinc. Its salts, which cause vivid crimson colors in flames, are used in pyrotechnics and in the production of flares.

Strontium titanate has an extremely high refractive index and an optical dispersion greater than a diamond’s. It has been used as a gemstone, though it is very soft.

Isotopes

Natural strontium is a mixture of four stable isotopes. There are 16 other unstable isotopes known to exist. Strontium-90 (90Sr) is the most important, with a half-life of 29 years. It is a product of nuclear fallout and its presence can cause health problems. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP (Systems for Nuclear Auxiliary Power) devices. These devices may be used in space vehicles, remote weather stations, navigational buoys, etc., as well as where a lightweight, long-lived, nuclear-electric power source is needed.

(Source: Los Alamos National Laboratory)

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