This groundbreaking work, the culmination of more than 10 years of research, presents a breakthrough theory of chemical bonding across the periodic table. Professor Epiotis, an internationally known and respected member of the theoretical community, challenges the conventional chemical concepts that underlie popular theories of chemical bonding. Building on his insight that electron-electron repulsion is the single crucial variable that differentiates one chemical system from another, the author formulates, explains, and applies a new approach based on nonorthogonal valence bond methodology that amounts to nothing less than a revolutionary unified theory of chemical boding across the periodic table. This work represents the first post-Pauling theory of chemical bonding. New theory means new formulae, and this work is about new chemical formulae that lead to the self-consistent rationalization of existing facts and, even more important, the design of new chemistry.