Strontium fluoride
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| strontium fluoride | |
|---|---|
| Other names | Strontium difluoride Strontium(II) fluoride |
| Identifiers | |
| CAS number | [7783-48-4] |
| EINECS number | |
| Properties | |
| Molecular formula | SrF2 |
| Molar mass | 125.62 g/mol |
| Density | 4.24 g/cm3 |
| Melting point |
1477 °C |
| Boiling point |
2460 °C |
| Solubility in other solvents | 0.039 g/100 g |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Strontium fluoride, SrF2, also called strontium difluoride and strontium(II) fluoride, is a fluoride of strontium. It is a stable brittle white crystalline solid with melting point of 1477°C and boiling point 2460°C.
Contents |
[edit] Preparation
Strontium fluoride is prepared by reaction of strontium chloride with fluorine gas, or by action of hydrofluoric acid on strontium carbonate.
[edit] Structure
The solid adopts the fluorite structure. In the vapour phase the SrF2 molecule is non-linear with an F-Sr-F angle of approximately 120°. [1] This is an exception to VSEPR theory which would predict a linear structure. Ab initio calculations have been cited to propose that contributions from d orbitals in the shell below the valence shell are responsible.[2] Another proposal is that polarisation of the electron core of the barium atom creates an approximately tetrahedral distribution of charge that interacts with the Sr-F bonds.[3]
[edit] Properties
It is almost insoluble in water (its Ksp value is approximately 4.33x10-9 at 25 degrees Celsius.
It irritates eyes and skin, and is harmful when inhaled or ingested.
Similar to CaF2 and BaF2, SrF2 displays superionic conductivity at elevated temperatures.[4]
Strontium fluoride is transparent to light in the wavelengths from vacuum ultraviolet (150 nm) to infrared (11 µm). Its optical properties are intermediate to calcium fluoride and barium fluoride.[5]
[edit] Uses
Strontium fluoride is used as an optical material for a small range of special applications, for example, as an optical coating on lenses and also as a thermoluminescent dosimeter crystal. Another use is as a carrier of strontium-90 radioisotope in radioisotope thermoelectric generators.
[edit] References
- ^ Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ Ab initio model potential study of the equilibrium geometry of alkaline earth dihalides: MX2 (M=Mg, Ca, Sr, Ba; X=F, Cl, Br, I)Seijo L.,Barandiarán Z J. Chem. Phys. 94, 3762 (1991) doi:10.1063/1.459748
- ^ Core Distortions and Geometries of the Difluorides and Dihydrides of Ca, Sr, and Ba Bytheway I, Gillespie RJ, Tang TH, Bader RF Inorganic Chemistry, Vol.34, No.9, 2407-2414, 1995 doi:10.1021/ic00113a023
- ^ http://www.newmet.co.uk/Products/koch/strontium.php
- ^ http://www.crystran.co.uk/products.asp?productid=155
