Fluoride is the reduced form of fluorine. Both organic and inorganic compounds containing the element fluorine are sometimes called fluorides. Fluoride, like other halides, is a monovalent ion (−1 charge).
Its compounds often have properties that are distinct relative to other halides. Structurally, and to some extent chemically, the fluoride ion resembles the hydroxide ion.
Fluorine-containing compounds range from potent toxins such as sarin to life-saving pharmaceuticals such as efavirenz, and from inert materials such as calcium fluoride to the highly reactive sulfur tetrafluoride.
The range of fluorine-containing compounds is considerable as fluorine is capable of forming compounds with all the elements except helium and neon.
Compounds containing fluoride anions and in many cases those containing covalent bonds to fluorine are called fluorides.
Few inorganic fluorides are soluble in water without undergoing
significant hydrolysis. Examples of inorganic fluorides include
hydrofluoric acid (HF), sodium fluoride (NaF), and uranium hexafluoride
(UF6).
In terms of its reactivity, fluoride differs
significantly from chloride and other halides, and is more strongly
solvated due to its smaller radius/charge ratio.
Its closest chemical
relative is hydroxide. The Si-F linkage is one of the strongest single
bonds. In contrast, other silyl halides are easily hydrolyzed.
Many fluoride minerals are known, but paramount in commercial importance
are fluorite and fluorapatite. Fluoride is found naturally in low
concentration in drinking water and foods.
Water with underground
sources is more likely to have higher levels of fluoride, whereas the
concentration in seawater averages 1.3 parts per million (ppm).
Fresh
water supplies generally contain between 0.01–0.3 ppm, while the ocean
contains between 1.2 and 1.5 ppm.
Further Reading
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