Strontium fluoride
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| Names | |
|---|---|
| Other names
Strontium difluoride Strontium(II) fluoride | |
| Identifiers | |
7783-48-4  | |
| 3D model (Jmol) | Interactive image |
| ChemSpider | 74190 |
| ECHA InfoCard | 100.029.091 |
| EC Number | 232-00-3 |
| PubChem | 82210 |
| |
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| Properties | |
| SrF2 | |
| Molar mass | 125.62 g/mol |
| Density | 4.24 g/cm3 |
| Melting point | 1,477 °C (2,691 °F; 1,750 K) |
| Boiling point | 2,460 °C (4,460 °F; 2,730 K) |
| 0.039 g/100 mL | |
| Refractive index (nD) |
1.439 @0.58 µm |
| Structure | |
| cubic crystal system, cF12 | |
| Fm3m, #225 | |
| Sr, 8, cubic F, 4, tetrahedral | |
| Hazards | |
| Flash point | Non-flammable |
| Related compounds | |
| Other anions |
Strontium chloride Strontium bromide Strontium iodide |
| Other cations |
beryllium fluoride magnesium fluoride calcium fluoride barium fluoride |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is ?) | |
| Infobox 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.
Preparation
Strontium fluoride is prepared by reaction of strontium chloride with fluorine gas, or by action of hydrofluoric acid on strontium carbonate.
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 polarization of the electron core of the strontium atom creates an approximately tetrahedral distribution of charge that interacts with the Sr-F bonds.[3]
Properties
It is almost insoluble in water (its Ksp value is approximately 2.0x10−10 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]
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.
References
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0-08-037941-9.
- ↑ 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
- ↑ https://web.archive.org/20051214052733/http://www.newmet.co.uk:80/Products/koch/strontium.php
- ↑ Mediatopia Ltd. "http://www.crystran.co.uk/strontium-fluoride-srf2.htm". Crystran.co.uk. Retrieved 2012-08-18. External link in
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