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Difluoride - Wikipedia

From Wikipedia, the free encyclopedia

(Redirected from Helium difluoride)

Order and disorder in difluorides

The fluorite structure	Beryllium fluoride glass

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

Metal difluorides are all ionic. Despite being highly ionic, the alkaline earth metal difluorides generally have extremely high lattice stability and are thus insoluble in water. The exception is beryllium difluoride. In addition, many transition metal difluorides are water-soluble.

Calcium difluoride is a notable compound. In the form of the mineral fluorite it is the major source of commercial fluorine. It also has an eponymic crystal structure, which is an end member of the spectrum starting from bixbyite and progressing through pyrochlore.

List of the difluorides

Examples of the difluorides include:

Alkaline earth metal difluorides

The alkaline earth metals all exhibit the oxidation state +2, and form difluorides. The difluoride of radium 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

Transition metal difluorides

Compounds of the form MF₂:

Post-transition metal difluorides

Nonmetal and metalloid difluorides

Noble gas difluorides

Bifluorides

The bifluorides contain the two fluorine atoms in a covalently bound HF₂⁻ polyatomic ion rather than as F⁻ anions.

Organic difluorides

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

References

^ 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 ^d Müller, 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.

Bibliography

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. Retrieved 3 March 2011.

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