The Conceptual Density Functional Theory: Origin and Development to Study Atomic and Molecular Hardness

In this chapter, we briefly discuss the origin and development of conceptual density functional theory (CDFT). We also review the method of calculating equalized molecular electronegativity, equalized molecular 2electrophilicity, and equalized molecular nucleophilicity based on the assumption of charge equalization during the chemical event of molecule formation and by combining the electrostatic theorem and CDFT.