elements in group 18 have complete outer electron shells on the periodic table of elements
one_of_chemical_elements is not helium. mercury_atom is not atom. electron_shell is not group. electron_shell is group. group_11_elements is coinage_metals. group_11_elements is not coinage_metals. electron is not particle. one_of_chemical_elements is not iridium. rubidium_atom is not atom. group_18_elements is not noble_gases.