Strontium bromide
Template:Use British English Template:Chembox Strontium bromide is a chemical compound with a formula Template:Chem2. At room temperature it is a white, odourless, crystalline powder. Strontium bromide imparts a bright red colour in a flame test, showing the presence of strontium ions. It is used in flares and also has some pharmaceutical uses.
Preparation
Template:Chem2 can be prepared from strontium hydroxide and hydrobromic acid.
Alternatively strontium carbonate can also be used as strontium source.
These reactions give hexahydrate of strontium bromide (Template:Chem2), which decomposes to dihydrate (Template:Chem2) at 89 °C. At 180 °C anhydrous Template:Chem2 is obtained.[1]
Structure
At room temperature, strontium bromide adopts a crystal structure with a tetragonal unit cell and space group P4/n. This structure is referred to as α-Template:Chem2 and is isostructural with [[europium(II) bromide|Template:Chem2]] and [[uranium diselenide|Template:Chem2]]. The compound's structure was initially erroneously interpreted as being of the [[Lead(II) chloride|Template:Chem2]] type,[2] but this was later corrected.[3][4]
Around 920 K (650 °C), α-Template:Chem2 undergoes a first-order solid-solid phase transition to a much less ordered phase, β-Template:Chem2, which adopts the cubic fluorite structure. The beta phase of strontium bromide has a much higher ionic conductivity of about 1 S/cm, comparable to that of molten Template:Chem2, due to extensive disorder in the bromide sublattice.[4] Strontium bromide melts at 930 K (657 °C).
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Distorted square antiprismatic coordination geometry of crystallographically independent strontium atom number 1
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Square antiprismatic coordination geometry of strontium number 2
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Flattened tetrahedral coordination geometry of bromine number 1
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Distorted tetrahedral coordination geometry of bromine number 2
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Tetrahedral coordination geometry of bromine number 3
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Tetrahedral coordination geometry of bromine number 4
See also
References
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- ↑ Dale L. Perry, Sidney L. Phillips: Handbook of Inorganic Compounds. CRC Press, 1995, Template:ISBN, (Template:Trim&pg=PA387 Strontium bromide, p. 387, at Google Books).
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