Appearance
Fluorine is a pale yellow, corrosive gas. It has a characteristic pungent odour, detectable at very low concentrations.

Source
Fluorine occurs mainly in the minerals Fluorspar and Cryolite, but is widely distributed in other minerals. it can be obtained by electrolysing a solution of Potassium hydrogen fluoride in anhydrous Hydrogen fluoride in a vessel of transparent Fluorspar.

Uses
Commercial production of Fluorine only began in World War II, when the production of the atom bomb and other nuclear energy projects made it necessary to produce large quantities. The element and its compounds are used in the production of Uranium and many fluorochemicals, including high-temperature plastics. Hydrofluoric acid is used for etching the glass of light bulbs and similar applications, and fluorochloro-hydrocarbons are used in air conditioning and refrigeration. The presence of fluorides below 2 parts per million in drinking water is believed to prevent dental cavities, but higher concentrations may cause mottled enamel in children acquiring permanent teeth.

General Information
Fluorine is the most reactive non-metal, and will combine with most other elements. Only a few of the Inert Gases do not combine with this element. It corrodes Platinum, a metal that resists most other chemicals. In a stream of Fluorine gas many substances burn with a bright flame, including finely divided metals, glass, ceramics, Carbon, wood, rubber and even water.

Fluorine and the fluoride ion are highly toxic.