Question

What is the valency of fluoride?

Answer 1

Fluorine is the chemical element with the symbol $F$ and atomic number $9$ and its electronic configuration is $[He]2{s^2}2{p^5}$. The atom of fluorine prefers to gain an electron to complete its last orbit.
Fluoride is the simplest fluorine anion. ${F^ - } + {H_2}O \rightleftharpoons HF + H{O^ - }$

Complete answer:
Fluoride is the negative anion of fluorine, it is an inorganic, monatomic anion of fluorine, with the chemical formula ${F^ - }$ it’s valency is $- 1$, fluoride salts are typically white or colorless. Fluoride salts typically have distinctive bitter tastes, and are odorless. Fluoride is a weak base since it is only partially associated in solution.
Fluoride can act as a base. it can combine with a proton ${H^ + }$.
${F^ - } + {H^ + } \to HF$ this neutralization reaction forms hydrogen fluoride, the conjugate acid of fluoride. In aqueous solution, fluoride has a $p{K_b}$ value of $10.8$. It is therefore a weak base, however upon prolonged contact with moisture, soluble fluoride salts will decompose to their respective hydroxides or oxides. ${F^ - } + {H_2}O \rightleftharpoons HF + H{O^ - }$.
Sources of fluoride:
$\bullet$ Fluoridated water- Countries like the US and the UK and Australia add fluoride to their public water supplies. In the US, fluoridated water generally contains $0.7$ parts per million.
$\bullet$ Groundwater- Groundwater naturally contains fluoride, but the concentration varies. Typically, it’s between $0.01 - 0.3$ parts per million, but in some areas dangerously high levels are present, this may cause serious health problems.
$\bullet$ Fluoride supplements- These are available as drops or tablets. Fluoride supplements are recommended for children over age $6$ months of age who have a high risk of developing cavities.
$\bullet$ Dental care products- fluoride is added to a number of dental care products on the market, such as toothpaste and mouth rinses.
Uses of fluoride,
Fluoride salts are hydrofluoric acid and are the main fluorides of industrial values. The main use of fluoride, in terms of volume, is in the production of cryolite, it is used in aluminum smelting. Fluoride-containing compounds, such as sodium fluoride or sodium monofluorophosphate are used in topical and systemic fluoride therapy for preventing tooth decay.

Note:
Most fluoride salts dissolve to give the bifluoride $(H{F^ - })$ anion. Sources of true ${F^ - }$ anions are rare because the highly basic fluoride anion abstracts protons from many sources. Relative unsolvated fluoride which does not exist in aprotic solvents is called “naked”.
Naked fluoride is a strong Lewis base , and a powerful nucleophile. Some quaternary ammonium salts of naked fluoride include tetramethylammonium fluoride and tetrabutylammonium fluoride.