- halogen - any of five related nonmetallic elements (fluorine or chlorine or bromine or iodine or astatine) that are all monovalent and readily form negative ions
--1 is a kind of group, grouping
--1 has particulars:astatine, At, atomic number 85; bromine, Br, atomic number 35; chlorine, Cl, atomic number 17; fluorine, F, atomic number 9; iodine, iodin, I, atomic number 53