A new and simple model of homopolar and heteropolar band gaps and ionicity is presented which overcomes the discrepancies of PVL (Philips, Van Vechten and Levine) theory and also of the other scales, results of which are not in conformity with the findings of hardness/bulk modulus reported in recent years. The proposed model requires the knowledge of bond length as the only input parameter and avoids the demand of additional parameters obtained from the detailed crystal structure as required in PVL theory. It has been applied to group-IV and IV-IV, IV-VI, III-V, II-VI and I-VII semiconductors of Zinc blende/wurtzite and rocksalt structures and group II-VI and I-VII ionic compounds of rocksalt and cesium chloride structures. It has also been utilised to evaluate ionicity of boron-boron bonds in B12 icosahedra. One critical and two sub-critical ionicities have also been proposed in this study. Besides, a new relation is proposed for direct evaluation of heteropolar band gap in terms of homopolar band gap of the materials studied. Results of the new model are in conformity with the trend of bulk modulus/ hardness reported and also of bond length. The proposed model has further been extended to ternary (I-III-VI2 and II-IV-V2) semiconductors and multibond high Tc – Superconductor, YBa2Cu3O7. Results obtained are quite reasonable.