Strontium fluoride, SrF2, also called strontium difluoride and strontium(II) fluoride, is a fluoride of strontium. It is a brittle white crystalline solid. In nature, it appears as the very rare mineral strontiofluorite.[2][3]
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| Names | |
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| Other names
Strontium difluoride
Strontium(II) fluoride | |
| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.029.091 |
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PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| SrF2 | |
| Molar mass | 125.62 g/mol |
| Density | 4.24 g/cm3 |
| Melting point | 1,473 °C (2,683 °F; 1,746 K) |
| Boiling point | 2,460 °C (4,460 °F; 2,730 K) |
| 0.117 g/100 mL | |
Solubility product (Ksp)
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4.33×10−9[1] |
| −37.2·10−6 cm3/mol | |
Refractive index (nD)
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1.439 @0.58 μm |
| Structure | |
| cubic crystal system, cF12 | |
| Fm3m, #225 | |
a = 5.80 Å, b = 5.80 Å, c = 5.80 Å α = 90°, β = 90°, γ = 90°
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| Sr, 8, cubic F, 4, tetrahedral | |
| Hazards | |
| Flash point | Non-flammable |
| Related compounds | |
Other anions
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Strontium chloride Strontium bromide Strontium iodide |
Other cations
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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).
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Preparation
editStrontium fluoride is prepared by the action of hydrofluoric acid on strontium carbonate.[4]
Structure
editThe solid adopts the fluorite structure. In the vapour phase the SrF2 molecule is non-linear with an F−Sr−F angle of approximately 120°.[5] 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.[6] 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.[7]
Properties
editIt 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.[8]
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.[9]
Uses
editStrontium 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
edit- ^ John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–189. ISBN 978-1138561632.
- ^ "Strontiofluorite".
- ^ "List of Minerals". 21 March 2011.
- ^ W. Kwasnik (1963). "Strontium Fluoride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. p. 234.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
- ^ 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
- ^ "Newmet Koch - Strontium". Archived from the original on 2005-12-14.
- ^ Mediatopia Ltd. "Strontium Fluoride (SrF2) Optical Material". Crystran.co.uk. Retrieved 2012-08-18.