halogen

¹hal·o·gen

noun \ˈha-lə-jən\

Definition of HALOGEN

: any of the five elements fluorine, chlorine, bromine, iodine, and astatine that form part of group VIIA of the periodic table and exist in the free state normally as diatomic molecules

— ha·log·e·nous \ha-ˈlä-jə-nəs\ adjective

Origin of HALOGEN

Swedish, from hal- + -gen

First Known Use: 1842

²halogen

adjective

Definition of HALOGEN

: containing, using, or being a halogen <a halogen lamp>

First Known Use of HALOGEN

1880

halo·gen

noun \ˈhal-ə-jən\   (Medical Dictionary)

Medical Definition of HALOGEN

: any of the five elements fluorine, chlorine, bromine, iodine, and astatine that form part of group VII A of the periodic table and exist in the free state normally as diatomic molecules

—ha·log·e·nous \ha-ˈläj-ə-nəs\ (audio pronunciation) adjective

halogen

noun    (Concise Encyclopedia)

Any of six nonmetallic elements—fluorine, chlorine, bromine, iodine, astatine, and element 117—with similar chemical properties. They occur in the second rightmost column of the periodic table as usually arranged. All are highly reactive oxidizing agents (see oxidation-reduction) with valence 1 (for fluorine, the only valence). They combine readily with most metals and nonmetals to form a variety of compounds and never occur uncombined in nature. A radioactive element, astatine occurs naturally in minute amounts as an intermediate decay product; it has no stable nonradioactive isotopes. Only a few atoms of element 117 have been artificially produced, and it is not found in nature. Halogen salts formed with metal atoms (halides) are very stable; sodium chloride is the most familiar. The halogen lamp takes its name from the halogens included in the gas within its tungsten-filament bulb, added to prolong filament life and increase brightness.