Strontium

Strontium

Strontium is a chemical element with symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. Strontium has physical and chemical properties similar to its two neighbors calcium and barium. It occurs naturally in the minerals celestine and strontianite. While natural strontium is stable, the synthetic 90Sr isotope is present in radioactive fallout and has a half-life of 28.90 years.

Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered in 1790 by Adair Crawford and William Cruickshank. The production of sugar from sugar beet was in the 19th century the largest application. Strontium compounds are today mostly used for the production of cathode ray tubes. The displacement of cathode ray tubes by other display methods in television sets is changing the overall consumption.

Occurrence


Strontium commonly occurs in nature, the 15th most abundant element on Earth, estimated to average approximately 360 parts per million in the Earth's crust and is found chiefly as the form of the sulfate mineral celestite (SrSO4) and the carbonate strontianite (SrCO3). Of the two, celestite occurs much more frequently in sedimentary deposits of sufficient size to make development of mining facilities attractive. Because strontium is used most often in the carbonate form, strontianite would be the more useful of the two common minerals, but few deposits have been discovered that are suitable for development.

The mean strontium content of ocean water is 8 mg/l. At a concentration between 82 and 90 µmol/l of strontium the concentration is considerable lower than the calcium concentration which is normally between 9.6 and 11.6 mmol/l.

Symbol		Sr
Atomic Number		38
Atomic Weight		87.62
Oxidation States		+2
Electronegativity, Pauling		0.95
State at RT		Solid, Metal
Melting Point, K		1042
Boiling Point, K		1657

Appearance and Characteristics

Harmful effects:

Strontium’s non-radioactive isotopes are considered non-toxic.

Characteristics:

• Strontium is a soft, silvery metal. When cut it quickly turns a yellowish color due to the formation of strontium oxide (strontia, SrO). Finely powdered strontium metal is sufficiently reactive to ignite spontaneously in air.
• It reacts with water quickly (but not violently like the Group 1 metals) to produce strontium hydroxide and hydrogen gas.
• Strontium and its compounds burn with a crimson flame and are used in fireworks.

Uses of Strontium

• Strontium is used for producing glass (cathode ray tubes) for color televisions. It is also used in producing ferrite ceramic magnets and in refining zinc.
• The world’s most accurate atomic clock, accurate to one second in 200 million years, has been developed using strontium atoms.
• Strontium salts are used in flares and fireworks for a crimson color.
• Strontium chloride is used in toothpaste for sensitive teeth.
• Strontium oxide is used to improve the quality of pottery glazes.
• The isotope 90Sr is one of the best long-lived, high-energy beta emitters known. It is used in cancer therapy.

Strontium metal burns in air with a distinctive red flame, forming a mixture of strontium oxide and nitride.

The world’s most accurate atomic clock, based on strontium atoms, would neither gain nor lose a second in more than 200 million years.