Chemical bonding in rock salt structured transition metal oxides

For oxides, MO ( M = Mg, Ca, Sr, Ba), the basicity moderating parameter of M governs the nature of the combined oxide(-II) ion, specifically (i) its Pauling electronegativity, x 0, and (ii) its electronic polarizability, α O 2− , so leading to a simple relationship between x 0 and α O 2− . This relationship is not obeyed by transition metal oxides ( M = Mn, Fe, Ni), but the chemical behavior of mixed molten oxide systems (slags) indicates that the discrepancy lies in x 0 and not in α O 2− . It is argued that this discrepancy arises because of the contribution to the heat of formation of M M bonding in these oxides. CdO and the metallic oxides TiO and VO are also considered.