Fluorine, F₂, is a gas and is the most reactive of all the nonmetals. Only a few of the noble gases resist reacting with fluorine. Platinum, a material that is inert towards most other chemicals, corrodes in the presence of fluorine. Because it is such a strong oxidizing agent that it has not been produced by chemical oxidation of F^- ions (i.e. after more than 170 years of trying). The pale yellow gas is prepared by electrolysis of a molten mixture of hydrogen fluoride and potassium fluoride.

There are many uses for fluorine. These include:

1. fluorine as a fluorinating agent.
2. the use of fluorinated organic compounds called fluorocarbons or chlorofluorocarbons (CFCs) as refrigerants, lubricants, plastics, insecticides, and aerosol propellants.
3. the use of Teflon, for nonstick surfaces on cooking utensils and in applications where inert surfaces are required. One such application is artificial valves for the heart.
4. the use of gaseous F₂ in the production of volatile uranium hexafluoride, UF₆, which is used for nuclear fuel,
5. the production of SF₆ for use as electrical insulator, and
6. F^- ions to prevent dental tooth decay, especially in children.