Halogen
the electro-negative radical of a haloid salt. This term is also used for the monad elements chlorine, bromine, iodine, and fluorine, as their sodium salts resemble sea salt, which is chloride of sodium, NaCl. Chloride is a gas, bromine a liquid, and iodine a solid at ordinary temperatures. Chlorine has the greatest chemical affinity for hydrogen, and iodine for oxygen, that of bromine being intermediate.