Fluorine

Fluorine's name comes from the Latin fluere, meaning to flow, because the element was originally found in the mineral fluorspar (fluorite, calcium fluoride, CaF₂) which melts when heated and was used in smelting and welding.  

The early chemists tried to isolate fluorine from fluorspar but without success. Then in 1886 the French chemist, Henri Moissan (1852-1907) obtained fluorine as a gas, F₂, by the electrolysis of a solution of potassium bifluoride (KHF₂) in anhydrous HF. Fluorine gas is still produced by this method in electrolytic cells made of Monel metal, a nickel-copper alloy, which resists attack by F₂.