A poisonous pale yellow gaseous element belonging to group 17 (formerly VIIB) of the periodic table (the halogens); a.n. 9; r.a.m. 18.9984; d. 1.7 g dm−3; m.p. –219.62°C; b.p. –188.1°C. The main mineral sources are fluorite (CaF2) and cryolite (Na3AlF). The element is obtained by electrolysis of a molten mixture of potassium fluoride and hydrogen fluoride. It is used in the synthesis of organic fluorine compounds. Chemically, it is the most reactive and electronegative of all elements. It is a highly dangerous element, causing severe chemical burns on contact with the skin. The element was identified by Karl Scheele in 1771 and first isolated by Henri Moissan in 1886.
https://www.webelements.com/fluorine/ Information from the WebElements site