Thermodynamic parameters and energy-band gap of a given metal oxide, are suitable measures of its stability. For this reason, direct correlations between energy-band gap or chemical hardness, and thermodynamic parameters (e.g. standard enthalpy of formation) have been constructed for different metal oxides. Furthermore, a simple relationship to calculate values of energy-band gaps, for metal oxides, from values of their enthalpies of formation, is presented here. When tested, an appreciable number of metal oxides from s- , p- and d-blocks well obeyed the relationship, while a number of metal oxides deviated. A qualitative theoretical account for such different behaviors is presented here.