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   Sr

STRONTIUM

(Strontian, town in Scotland)

Sr at. wt. 87.62
   at. no. 38 
   m.p. 769°C 
   b.p. 1384°C
   sp. gr. 2.54
   valence 2.
Electronic configuration
 SHELL  K L M N O P Q
 SUB  SHELL He Neon Argon Krypton Xenon Radon Eka-radon
1s 2s 2p 3s 3p 3d 4s 4p 4d 5s 5p 4f 5d 6s 6p 5f 6d 7s 7p
Strontium 1s22s22p63s23p63d104s24p64d05s2    
Symbol 2S0
Strontium was discovered by Davy by electrolysis in 1808. Strontium is found chiefly as celestite (Sr504) and stron-tianite (Sr03). The metal can be prepared by electrolysis of the fused chloride mixed with potassium chloride, or is made by reducing strontium oxide with aluminum in a vacuum at a temperature at which strontium distills off. Three allotropic forms of the metal exist, with transition points at 2350C and 5400C. Strontium is softer than calcium and decomposes water more vigorously. It does not absorb nitrogen below 3800C. It should be kept under kerosene to prevent oxidation. 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 a beautiful crimson color to flames, and these salts are used in pyrotechnics. Natural strontium is a mi~ture of four stable isotopes. Twelve other unstable isotopes are known to exist. Of greatest importance is Sr90 with a half-life of 28 yrs. It is a prQduct of nuclear fallout and presents a health problem. This isotope is one of the best long-lived high-energy beta emitters known, and is used in SNAP devices (Systems for Nuclear Auxiliary Power). These devices hold promise' for use in space vehicles, remote weather stations, navigational buoys, ets. 'where a light-weight, long-lived, nuclear-electric power source is needed. Strontium hydroxide, has been used in sugar refining; however lime is replacing its use as it is cheaper. Strontium titanate is an intetesting optical material as it has an extremely high refiactive index and an optical dispersion greater than that of diamond. It has been used as a gemstone, but it is very soft. It does not occur naturally. The applications of strontium are similar to those of barium and calcium, but there are few advantages and the cost is much higher. Strontium metal costs about 56 to $8/lb.

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