question 4) Which of following elements are nonmetals? Na O Ar S only And IV III, and IV only An atom having an atomic number of 12 needs how many erected 6 9 Solution Answer:C. II, III and IV Explanation: The nonmetal elements are the elements with relatively low boiling points, that are poor conductors of heat and electricity, and that do not readily give up their electrons. The 17 nonmetal elements are: hydrogen, helium, carbon, nitrogen, oxygen, fluorine, neon, phosphorus, sulfur, chlorine, argon, selenium, bromine, krypton, iodine, xenon, and radon..