The Halogens - Properties . The halogens are the only group of the Periodic Table which have solid , liquid and gaseous elements at room temperature .
Fluorine is an extremely reactive pale yellow gas .
Chlorine is a reactive yellow-green gas . Bromine is a less reactive red-brown liquid . Iodine is a still less reactive dark grey solid. When iodine is heated , it Sublimes to become a gas with a purple vapour .