Strontium bromide is a

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with a formula . At room temperature it is a white, odourless, crystalline powder. Strontium bromide imparts a bright red colour in a

flame test A flame test is relatively quick test for the presence of some elements in a sample. The technique is archaic and of questionable reliability, but once was a component of qualitative inorganic analysis. The phenomenon is related to pyrotechnics ...

, showing the presence of strontium ions. It is used in

flares A flare, also sometimes called a fusée, fusee, or bengala, bengalo in several European countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illuminatio ...

and also has some pharmaceutical uses.

Preparation

can be prepared from

strontium hydroxide Strontium hydroxide, Sr(OH)2, is a caustic alkali composed of one strontium ion and two hydroxide ions. It is synthesized by combining a strontium Salt (chemistry), salt with a strong base. Sr(OH)2 exists in anhydrous, hydrate, monohydrate, or oct ...

and

hydrobromic acid Hydrobromic acid is an aqueous solution of hydrogen bromide. It is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains ...

. : Alternatively

strontium carbonate Strontium carbonate (SrCO3) is the carbonate salt of strontium that has the appearance of a white or grey powder. It occurs in nature as the mineral strontianite. Chemical properties Strontium carbonate is a white, odorless, tasteless powder ...

can also be used as

strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...

source. : These reactions give

hexahydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

of strontium bromide (), which decomposes to dihydrate () at 89 °C. At 180 °C

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achie ...

is obtained.Dale L. Perry, Sidney L. Phillips: ''Handbook of Inorganic Compounds''. CRC Press, 1995, , ().

Structure

At room temperature, strontium bromide adopts a

crystal structure In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from intrinsic nature of constituent particles to form symmetric patterns that repeat ...

with a

tetragonal In crystallography, the tetragonal crystal system is one of the 7 crystal systems. Tetragonal crystal lattices result from stretching a cubic lattice along one of its lattice vectors, so that the Cube (geometry), cube becomes a rectangular Pri ...

unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector In mathematics, a unit vector i ...

and

space group In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...

''P''4/''n''. This structure is referred to as α- and is

isostructural Isostructural chemical compounds have similar chemical structures. " Isomorphous" when used in the relation to crystal structures is not synonymous: in addition to the same atomic connectivity that characterises isostructural compounds, isomorphous ...

with and . The compound's structure was initially erroneously interpreted as being of the type, but this was later corrected. Around 920 K (650 °C), α- undergoes a first-order solid-solid

phase transition In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic Sta ...

to a much less ordered phase, β-, which adopts the cubic

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...

structure. The beta phase of strontium bromide has a much higher ionic conductivity of about 1 S/cm, comparable to that of molten , due to extensive disorder in the

bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retard ...

sublattice A lattice is an abstract structure studied in the mathematical subdisciplines of order theory and abstract algebra. It consists of a partially ordered set in which every pair of elements has a unique supremum (also called a least upper boun ...

. Strontium bromide melts at 930 K (657 °C). File:Strontium-bromide-xtal-3D-sf.png,

Space-filling model In chemistry, a space-filling model, also known as a ''calotte model'', is a type of three-dimensional (3D) molecular model where the atoms are represented by spheres whose radii are proportional to the radii of the atoms and whose center-to- ...

of the packing of and ions in α- File:Strontium-bromide-xtal-Sr1-coordination-view-2-3D-bs-17-25.png, Distorted square antiprismatic

coordination geometry The coordination geometry of an atom is the geometrical pattern defined by the atoms around the central atom. The term is commonly applied in the field of inorganic chemistry, where diverse structures are observed. The coordination geometry depen ...

of crystallographically independent strontium atom number 1 File:Strontium-bromide-xtal-Sr2-coordination-view-2-3D-bs-17-25.png, Square antiprismatic coordination geometry of strontium number 2 File:Strontium-bromide-xtal-Br1-coordination-3D-bs-17-25.png, Flattened tetrahedral coordination geometry of bromine number 1 File:Strontium-bromide-xtal-Br2-coordination-3D-bs-17-25.png, Distorted tetrahedral coordination geometry of bromine number 2 File:Strontium-bromide-xtal-Br3-coordination-3D-bs-17-25.png, Tetrahedral coordination geometry of bromine number 3 File:Strontium-bromide-xtal-Br4-coordination-3D-bs-17-25.png, Tetrahedral coordination geometry of bromine number 4

References

* http://www.webelements.com/ {{bromine compounds Strontium compounds Bromides Alkaline earth metal halides

Preparation

Structure

See also

References