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. Beryllium difluoride Magnesium fluoride Calcium fluoride Strontium difluoride Barium fluoride Radium fluoride
{ | class="wikitable sortable" |+ Solubility-related constants of alkaline earth metal fluorides ! Metal ! M2+ HE ! F− HE ! "MF2" unitHE ! MF2 latticeenergies (−kJ/mol) ! Solubility(mol/L) |- | 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
Samarium difluoride
Europium difluoride
Ytterbium difluoride
Transition metal difluorides
Compounds of the form MF2: Cadmium difluoride Chromium(II) fluoride Cobalt difluoride Copper(II) fluoride Iron(II) fluoride Manganese(II) fluoride Mercury difluoride Nickel difluoride Palladium difluoride Silver difluoride Zinc difluoride
Post-transition metal difluorides
Lead difluoride
Tin(II) fluoride
Nonmetal and metalloid difluorides
Dinitrogen difluoride
Oxygen difluoride
Dioxygen difluoride
Selenoyl difluoride
Sulfur difluoride
Disulfur difluoride
Thionyl difluoride
Germanium difluoride
Noble gas difluorides
Helium difluoride (hypothetical) Argon difluoride (predicted) Krypton difluoride Xenon difluoride Radon difluoride
Bifluorides
The bifluorides contain the two fluorine atoms in a covalently bound HF2− polyatomic ion rather than as F− anions. Ammonium bifluoride Potassium bifluoride Sodium bifluoride
Organic difluorides
Ethanedioyl difluoride
Ethylidene difluoride
Carbonyl difluoride
Carbon dibromide difluoride (dibromodifluoromethane) Carbon dichloride difluoride (dichlorodifluormethane) Methyl difluoride Methylphosphonyl difluoride Polyvinylidene difluoride