- Fluorine (F) is a highly reactive nonmetal and the lightest member of the halogen group, with atomic number 9 and positioned in Group 17 of the periodic table.
- It has seven valence electrons, needing only one more to complete its outer shell, which makes it the most electronegative and chemically reactive element known. Its atomic structure consists of nine protons, typically ten neutrons, and nine electrons arranged in two shells (two in the inner shell and seven in the outer shell).
- Fluorine has only one stable isotope, fluorine-19 (¹⁹F), though several short-lived radioactive isotopes are known.
- Under standard conditions, fluorine exists as a pale yellow diatomic gas (F₂) with a pungent odor, and it is highly toxic and corrosive.
- Fluorine is relatively rare in the universe, formed in small amounts in certain stellar environments through complex nucleosynthetic processes, possibly in asymptotic giant branch (AGB) stars, supernovae, and during interactions involving cosmic rays. On Earth, due to its extreme reactivity, fluorine is never found in its elemental form in nature; instead, it occurs in minerals such as fluorite (CaF₂), cryolite (Na₃AlF₆), and fluorapatite (Ca₅(PO₄)₃F). These minerals are the main commercial sources of fluorine compounds, particularly for the production of hydrofluoric acid (HF) and fluorinated materials.
- The isolation of elemental fluorine proved exceptionally difficult and dangerous because of its reactivity with virtually all other substances, including glass and water. Early attempts in the 19th century often resulted in severe chemical burns or fatalities. French chemist Henri Moissan successfully isolated fluorine in 1886 by electrolyzing potassium bifluoride (KHF₂) dissolved in anhydrous hydrogen fluoride (HF), using a specially designed apparatus. His achievement earned him the 1906 Nobel Prize in Chemistry.
- Fluorine and its compounds have significant industrial and technological importance. Hydrofluoric acid is essential in the production of fluorocarbons, in glass etching, and in the purification of uranium for nuclear fuel through uranium hexafluoride (UF₆). Fluoropolymers such as polytetrafluoroethylene (PTFE, Teflon) are valued for their chemical inertness, low friction, and heat resistance, finding uses in cookware, aerospace, and electrical insulation. In metallurgy, fluorides are used as fluxes to lower the melting point of ores. The addition of fluoride ions to drinking water and toothpaste in small amounts helps prevent dental cavities by strengthening tooth enamel, though the practice remains debated in some regions.
- Chemically, fluorine’s extreme reactivity allows it to form compounds with almost all elements, including some noble gases like xenon and krypton under special conditions. It can ignite hydrogen spontaneously at room temperature and react explosively with many organic materials. In biological systems, fluorine is not an essential element, but fluorinated compounds, including certain pharmaceuticals and agrochemicals, are important for their enhanced metabolic stability and bioactivity.
- Despite its many uses, fluorine and its compounds can be hazardous. Elemental fluorine gas is extremely toxic and corrosive, causing severe chemical burns upon contact. Hydrofluoric acid is particularly dangerous, as it penetrates tissues deeply and can bind calcium in the blood, leading to potentially fatal hypocalcemia. Proper safety protocols, including specialized equipment and training, are essential when handling fluorine.
