About Fluorides

Fluoride IonThe fluoride ion is the anion of fluorine, F-, and fluorides are compounds which contain this anion. Metallic mono-, di, and trifluorides usually exhibit ionic bonding, pentafluorides and higher exhibit covalent bonding, and tetrafluorides contain bonds with intermediate properties. Ionic-bonded fluorides may be soluble or insoluble: alkali fluorides are soluble, alkali earth metals form insoluble fluorides, transition metal difluorides are often soluble, and trifluorides are insoluble. An exception to some of these trends is beryllium difluoride, which features bonds with partially covalent character and the crystalline structure of a covalently bonded network solid, yet is soluble in water.

Covalently metal-bonded fluorides are typically either gases or volatile liquids or solids, and act chemically as oxidants and fluoridating agents. Tungsten hexafluoride is used routinely to deposit tungsten using chemical vapor deposition methods in semiconductor device fabrication. Uranium hexafluoride is of vital importance to the enrichment processed used to produce nuclear reactor fuels and material for nuclear weapons. Non-metal fluorides also exist, and all are volatile compounds, but their chemical properties vary widely. A number of important superacids contain fluorine, and are typically produced by mixing hydrogen fluoride, itself a highly reactive acid, with a metal fluoride.