An Etymological Dictionary of Astronomy and Astrophysics

A member of a group of five chemical elements having closely related and similar
properties. The halogens are: fluorine, chlorine, iodine, bromine, and astatine. They make up Group 17 of the → periodic table and can be found on the left-hand side of the → noble gases.

See also: From Gk. halo- prefix from Gk. hals “salt” + → -gen.