Fluorine is a pale yellow diatomic gas at room temperature. Indeed fluorine, the most electronegative element, will combine with almost every other element, including some of the noble gases.

Fluorine usually occurs as fluorspar (fluorite), CaF₂ and cryolite, Na₃AlF₆. These deposits are generally quite thin and are rarely economically workable. Sometimes these fluoride –containing ores occur as semiprecious minerals, which are mined, polished and used for their appearance rather than the fluoride they contain.

Extracting the halogen from their sources leads to difficulties due to their powerful oxidizing tendencies. They are usually obtained by oxidation of the halide ion, but in the case of fluoride there is no oxidizing agent strong enough to be used in the extraction process and so the oxidation is performed by electrolysis. The electrolysis is carried out using potassium fluoride dissolved in liquid anhydrous hydrogen fluoride, as the fluorine produced would react with water. A graphite anode and steel cathode is used.

Properties
Fluorine is the most electronegative of all elements known. It shows only –1 oxidation state, it does not show higher/variable oxidation states because it does not have d–orbitals in its valence shell.

Fluorine is a pale yellow gas at room temperature. Elemental fluorine is highly toxic.

Fluorine is a small atom, hence its nine electrons are firmly bound. It is difficult to remove electrons. Therefore fluorine has the highest ionization energy in the group. Fluorine can replace other halogens from halide compounds either in solution phase or even in dry state.

HF exits as a liquid due to hydrogen bonding between HF molecules, it acts as a weak acid due to the strong H–F bond.

Fluorine is such a powerful oxidizing agent that it reacts with water, producing oxygen and hydrogen fluoride. HF is a very dangerous fuming acid.

HF are corrosive and hence extreme care should be taken while working with them. Out of all the hydrohalic acids, HF attacks glass and hence it is used for etching glass and manufacture of glass shell for television tubes.

Uses of glass

• Fluoride ion, used widely in fluorination of water, under controlled conditions, inhibits tooth decay.
• Covalently bound fluorine–carbon compounds are known as fluorocarbons. These substances are very inert and strong oxidizing agents.
• Teflon, the most resistant material important in industry is a polymer of fluorine (–CF₂–CF₂)_n– polytetrafluoroethylene. It has very good thermo stability and is therefore used as a coating material.
• Some fluorinated derivatives of methane are used as refrigerants (commercially known as chlorofluorcarbons, freons).