Physical properties of the group 15 elements

Table 1.1 lists selected physical properties of the group 15 elements. Some observations regarding ionization energies are that:

• they increase rather sharply after removal of the p, electrons;
• they decrease only slightly between P and As (similar behaviour to that between Al and Ga, and between Si and Ge);
• for removal of the s electrons, there is an increase between Sb and Bi, just as between In and Tl, and between Sn and Pb.

     Values of Δ_aH^o decrease steadily from N to Bi, paralleling similar trends in groups 13 and