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Names | |
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Other names Strontium difluoride Strontium(II) fluoride | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
ECHA InfoCard | 100.029.091 |
EC Number |
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PubChem CID | |
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) | 4.33×10−9 [1] |
−37.2·10−6 cm3/mol | |
Refractive index (nD) | 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° | |
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). |
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]
Strontium fluoride is prepared by the action of hydrofluoric acid on strontium carbonate. [4]
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°. [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]
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. [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]
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.