fluorideion

Fluoride ion, sometimes written as fluorideion, is the anion F−, the negatively charged form of fluorine. It forms when a fluorine atom gains one electron. In aqueous solutions and many compounds, fluoride exists primarily as the fluoride ion. It is present in natural environments such as fluorite minerals, groundwater, and seawater, and it is widely used in industry and public health.

Chemistry and properties: Fluoride ion is a small, highly hydrated anion with a −1 charge. It is the conjugate base of hydrofluoric acid (HF), which has a pKa of about 3.17 at 25°C, making F− a relatively weak base in water. Fluoride forms salts with many cations, including sodium fluoride (NaF) and potassium fluoride (KF). It can act as a nucleophile in organic reactions, and in concentrated forms it can form sparingly soluble fluorides with certain metals, such as calcium fluoride (CaF2).

Occurrence and production: Naturally, fluoride occurs in minerals such as fluorite (CaF2) and can be found in trace amounts in groundwater and ocean water. Industrially, fluoride ions are produced from fluorides or hydrofluoric acid (HF). Common routes include generating alkali fluorides from HF or applying fluoride-containing minerals in processes linked to aluminum production and glass etching.

Applications and safety: Fluoride ion is used in public health to reduce dental caries, via water fluoridation and fluoride-containing dental products. It also serves as a reagent in chemical synthesis and various industrial processes. Excessive fluoride exposure can lead to dental or skeletal fluorosis and acute toxicity, so regulatory guidelines limit fluoride levels in drinking water and consumer products.