Fluorine is a yellowish, poisonous, highly corrosive gas.
It is the most chemically active nonmetallic element and is the most electronegative of all the elements. Fluorine is a member of group VIIa of the periodic table . It readily displaces the other halogens from their salts. Fluorine reacts with most inorganic and organic compounds. With hydrogen it forms hydrogen fluoride gas, whose water solution is called hydrofluoric acid.