In this work a systematic account of the concepts and the trends in the development of electronegativity, a fundamental property of atoms, ions, groups, bonds and molecules is given. Some important applications of the concept of electronegativity in the chemical world are also discussed. We have also calculated the molecular electronegativity, internuclear distance, atomic polar tensor, bond energy, standard enthalpies of formation, dipole charge, and dipole moment of some extremely ionic compounds and covalent molecules. As some dimensional inconsistencies in the formulae for the evaluation of bond energy and standard enthalpies of formation are found, we have suggested semi-empirical formulae for them.