| − | A [[halogen]] is any element that sits in column 17 of the periodic table. The known halogens are [[fluourine]], [[chlorine]], [[bromine]], [[iodine]] and the extremely rare and unstable [[astatine]]. | + | A [[halogen]] is any element that sits in column 17 of the periodic table. The known halogens are [[fluorine]], [[chlorine]], [[bromine]], [[iodine]] and the extremely rare and unstable [[astatine]]. |