What is the X in X-mas?
A compound, such as a fluorocarbon, that consists of carbon combined with one or more halogens. Halocarbons are typically nonflammable and nonreactive, though some halocarbons are broken down by ultraviolet radiation in the upper atmosphere, and this process releases free halogen atoms that damage the ozone layer. Some halocarbons have also been implicated as greenhouse gases.
any chemical compound of the element carbon and one or more of the halogens (bromine, chlorine, fluorine, iodine); two important subclasses of halocarbons are the chlorocarbons, containing only carbon and chlorine, and the fluorocarbons, containing only carbon and fluorine. Examples of chlorocarbons are carbon tetrachloride and tetrachloroethylene; the best known fluorocarbon is the resin polytetrafluoroethylene, called Teflon. Several, but not all, of the Freons (q.v.) are halocarbons, as is the resin polychlorotrifluoroethylene (q.v.; Kel-F). The nonflammability, low chemical reactivity, and low toxicity of many of the halocarbons are their most valuable properties (see organohalogen compound).