A group of elements in the periodic table: nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi), which all have outer electronic configurations ns2np3 with no partly filled inner levels. Formerly, they were classified in group V, which consisted of two subgroups: group VB (the main group) and group VA. Group VA consisted of vanadium (V), niobium (Nb), and tantalum (Ta), which are generally considered with the transition elements:
The lighter elements (N and P) are nonmetals; the heavier elements are metalloids. The lighter elements are electronegative in character and have fairly large ionization energies. Nitrogen has a valency of 3 and tends to form covalent compounds. The other elements have available d-sublevels and can promote an s-electron into one of these to form compounds with the V oxidation state. Thus, they have two oxides P2O3, P2O5, Sb2O3, Sb2O5, etc. In the case of bismuth, the pentoxide Bi2O5 is difficult to prepare and unstable – an example of the increasing stability of the III oxidation state in going from phosphorus to bismuth. The oxides also show how there is increasing metallic (electropositive) character down the group. Nitrogen and phosphorus have oxides that are either neutral (N2O, NO) or acidic. Bismuth trioxide (Bi2O3) is basic. Bismuth is the only member of the group that forms a well-characterized positive ion Bi3+.