Halogen

Halogen, any of the group of 5 elements consisting of fluorine, chlorine, bromine, iodine and astatine. These make up group VIIa of the Periodic Table and are highly reactive nonmetals. Apart from astatine, which is radioactive, the halogens are common elements and form many compounds with one another and with other elements. In their pure form, the halogens form molecules composed of 2 atoms.

See also: Element.