While the chemical situation of the purely covalent template crb (C1) 4 (C2) 4 is clear, the BX family exhibits different types of chemical bonding, changing from nitride to an ionocovalent behavior for P and As, and finally to borides in the case of Sb and Bi. It is also important to note that the steric factor plays an important role in these changes, as there is a regular increase in the atomic radius of pnictogen along the series.