 
Fluorine is element number 9 on the periodic table.
A fluorine molecule F2 is made up of two fluorine atoms held together by a covalent bond. Fluorine is a pale yellow gas at room temperature with a sharp, pungent odour. It is the most electronegative element, and is highly toxic, corrosive, and oxidizing.
Fluorine is the most reactive element, combining with all other elements except helium and neon.
 Fluoride is an essential ion for animals, strengthening bones and teeth. It is added to drinking water and toothpaste.
Fluorite (CaF2), also known as fluorspar, is a mineral that is abundant worldwide, and is the main source of fluoride, and hence fluorine. China and Mexico are the major suppliers. Fluorspar is also used in the production of steel, aluminum, glass, and cement. Fluorocarbon gases are greenhouse gases with very high global-warming potentials, up to 23,500 times that of carbon dioxide. Organofluorine compounds often persist in the environment due to the strength of the carbon–fluorine bond. Fluorine has no known role in the metabolism of mammals; a few plants and marine sponges synthesize organofluorine poisons that help deter predators. Hydrofluoric acid is a weak acid at low concentrations. However, it can attack glass, something that other acids cannot do. |