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Difluoride

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From Wikipedia, the free encyclopedia

(Redirected fromHelium difluoride)

Not to be confused withBifluoride.

Order and disorder in difluorides

The fluorite structure	Beryllium fluoride glass

Difluorides are chemical compounds with twofluorine atoms per molecule (or per formula unit).

Metal difluorides are allionic. Despite being highly ionic, thealkaline earth metal difluorides generally have extremely high lattice stability and are thusinsoluble in water. The exception isberyllium difluoride. In addition, manytransition metal difluorides are water-soluble.

Calcium difluoride is a notable compound. In the form of the mineralfluorite it is the major source of commercial fluorine. It also has an eponymic crystal structure, which is an end member of the spectrum starting frombixbyite and progressing throughpyrochlore.

List of the difluorides

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Examples of the difluorides include:

Alkaline earth metal difluorides

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The alkaline earth metals all exhibit the oxidation state +2, and form difluorides. The difluoride ofradium is however not well established due to the element's high radioactivity.

Solubility-related constants of alkaline earth metal fluorides
Metal	M²⁺HE^[1]	F⁻ HE^[2]	"MF₂" unit HE	MF₂ lattice energies (−kJ/mol)^[3]	Solubility (mol/L)^[4]
Be	2,455	458	3,371	3,526	25
Mg	1,922	458	2,838	2,978	0.0012
Ca	1,577	458	2,493	2,651	0.0002
Sr	1,415	458	2,331	2,513	0.0008
Ba	1,361	458	2,277	2,373	0.006

Lanthanide difluorides

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Transition metal difluorides

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Compounds of the form MF₂:

Thebifluorides contain the two fluorine atoms in acovalently bound HF₂⁻polyatomic ion rather than as F⁻ anions.

Organic difluorides

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Ethanedioyl difluoride
Ethylidene difluoride
Carbonyl difluoride
Carbon dibromide difluoride (dibromodifluoromethane)
Carbon dichloride difluoride (dichlorodifluormethane)
Methyl difluoride
Methylphosphonyl difluoride
Polyvinylidene difluoride

References

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^Wiberg, Wiberg & Holleman 2001, pp. XXXVI–XXXVII.
^Wiberg, Wiberg & Holleman 2001, p. XXXVI.
^Lide 2004, p. 12-23.
^Wiberg, Wiberg & Holleman 2001, p. 1073.
^^a ^b ^c ^dMüller, Bernd G. (1991). "Lanthanide Fluorides".Synthesis of Lanthanide and Actinide Compounds. Vol. 2. pp. 55–65.doi:10.1007/978-94-011-3758-4_2.
^Georg Brauer: Handbuch der Präparativen Anorganischen Chemie. 3., umgearb. Auflage. Band I. Enke, Stuttgart 1975,ISBN 3-432-02328-6, p. 255.
^Wu, R. Q."HeF2 and ArF2 molecules from first-principles study"

Bibliography

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Greenwood, N. N.; Earnshaw, A. (1998).Chemistry of the Elements (second ed.). Butterworth Heinemann.ISBN 0-7506-3365-4.
Lide, David R. (2004).Handbook of chemistry and physics (84th ed.). CRC Press.ISBN 0-8493-0566-7.
Wiberg, Egon; Wiberg, Nils; Holleman, Arnold Frederick (2001).Inorganic chemistry. Academic Press.ISBN 978-0-12-352651-9. Retrieved3 March 2011.

Index of chemical compounds with the same name

Thisset index article listschemical compounds articles associated with the same name.
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