halogen hal·o·gen (hāl'ə-jən)
Any of a group of five chemically related nonmetallic elements including fluorine, chlorine, bromine, iodine, and astatine.
|halogen (hāl'ə-jən) Pronunciation Key
Any of a group of five nonmetallic elements with similar properties. The halogens are fluorine, chlorine, bromine, iodine, and astatine. Because they are missing an electron from their outermost shell, they react readily with most metals to form salts. See Periodic Table.