Because the elements in group 7A are good at forming salts, the are called HALOGENS; the word 'halogen' mean SALT FORMERS. The halogens refers to the five non metallic elements that are found in group 7A, these are chlorine, bromine, iodine, fluorine and astatine. Each of these elements has seven electrons in their outermost shell and will readily react with metals to form ionic compounds. They all have oxidation number of -1.