Which group of the Periodic Table contains two elements that are gases at STP? Among the halogens, fluorine (F) and chlorine (Cl) are gases at STP. In the new, IUPAC approved system, the halogens are placed in group 17. In the two (ambiguous) older syste…ms, their group might be labelled VIIB or VIIA. Making the world better, one answer at a time.