In contrast element neon [Ne] has seven electrons in the valence shell and hence, does not i.e. in the same group as the other 3 elements i.e. [Ar],[Kr],[Xe]. In a family all elements have same outermost electronic configuration. Since, [Ne]3s23p3, chlorine belongs to halogen family while the remaining three are in same group i.e. group 12 (noble gas).