Strontium fluoride

Strontium fluoride
Names
	Other names Strontium difluoride; Strontium(II) fluoride
Identifiers
CAS Number	7783-48-4 ;
3D model (JSmol)	Interactive image;
ChemSpider	74190 ;
ECHA InfoCard	100.029.091
EC Number	232-00-3;
PubChem CID	82210;
UNII	EFY8GJS81Z ;
CompTox Dashboard (EPA)	DTXSID20894160 ;
	InChI InChI=1S/2FH.Sr/h21H;/q;;+2/p-2 Key: FVRNDBHWWSPNOM-UHFFFAOYSA-L ; InChI=1/2FH.Sr/h21H;/q;;+2/p-2 Key: FVRNDBHWWSPNOM-NUQVWONBAO;
	SMILES [Sr+2].[F-].[F-];
Properties
Chemical formula	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)
Solubility in water	0.117 g/100 mL
Solubility product (Ksp)	4.33×10−9
Magnetic susceptibility (χ)	−37.2·10−6 cm3/mol
Refractive index (nD)	1.439 @0.58 μm
Structure
Crystal structure	cubic crystal system, cF12
Space group	Fm3m, #225
Lattice constant	a = 5.80 Å, b = 5.80 Å, c = 5.80 Å α = 90°, β = 90°, γ = 90°
Coordination geometry	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 brittle white crystalline solid. In nature, it appears as the very rare mineral strontiofluorite.^[2]^[3]

Preparation

Strontium fluoride is prepared by the action of hydrofluoric acid on strontium carbonate.^[4]

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°.^[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

It is almost insoluble in water (its K_sp 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

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

^ 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.

[crc-1] John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99 ed.). CRC Press. pp. 5–189. ISBN 978-1138561632.

[Mindat-2] "Strontiofluorite".

[IMA-3] "List of Minerals". 21 March 2011.

[4] 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-5] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

[6] 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

[7] 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-8] "Newmet Koch - Strontium". Archived from the original on 2005-12-14.

[http://www.crystran.co.uk/strontium-fluoride-srf2.htm-9] Mediatopia Ltd. "Strontium Fluoride (SrF2) Optical Material". Crystran.co.uk. Retrieved 2012-08-18.

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