halogen
/ˈhalədʒ(ə)n
/ /ˈheɪlədʒ(ə)n/noun Chemistry
1Any of the elements fluorine, chlorine, bromine, iodine, and astatine, occupying group VIIA (17) of the periodic table. They are reactive non-metallic elements which form strongly acidic compounds with hydrogen from which simple salts can be made.For many syntheses, this means using such compounds as hydrocarbons and alcohols, plus inorganic acids, metals, halogens, or other compounds....
- The oxidation number of the halogens other than fluorine is - 1, unless they are bonded to oxygen or a more electronegative halogen.
- Four important chemical family names of elements still widely used are the alkali metals, the alkaline earths, the halogens, and the noble gases.
1.1 [as modifier] Denoting lamps and radiant heat sources using a filament surrounded by the vapour of iodine or another halogen: a halogen bulb...
- The light source was a halogen lamp and light intensity was varied with neutral density filters.
- The light source was a microscope halogen lamp, which unilaterally illuminated the protruding stump, via a light guide at a site 2-4 cm from the lower cut end.
- In this treatment, the patient is secured to a dentist chair with leather straps and an extremely hot halogen lamp is left inches from their face for hours at a time.
Derivatives
halogenic
- A live television camera and halogenic headlights allow positive identification of the target prior to detonation.
- Association of halogenic minerals here is very poor: it consists of gypsum, calcite and sepiolite.
- Volcanogenous rocks are found among halogenic formations so commonly that they, together with anhydrite, gypsum and limestone, may be considered as component part of these formations.
Origin
Mid 19th century: from Greek hals, halo- 'salt' + -gen.