Chapter 6 - Quantum Chemistry

Abstract

The purpose of this chapter is to explain quantum chemistry. As a matter of fact, nothing that pertains to either chemical reactivity or interaction has emerged. Only background material has been developed and the quantum behavior of real chemical systems remains to be explored. If quantum theory is to elucidate chemical effects, it goes beyond an analysis of atomic hydrogen. It deals with all types of atom, molecules, and ions, and explains their interaction with each other and predicts the course of chemical reactions as a function of environmental factors. It is not the same as providing the classical models of chemistry with a quantum-mechanical gloss, but destined to obscure the nonclassical features of molecular systems. The difficulty of finding a link between classical and quantum variables in chemistry is well documented. The failure of classical mechanics in the analysis of physical phenomena, such as blackbody radiation, is routinely discussed in elementary texts to emphasize the need of a quantum theory. The failure of classical mechanics to deal correctly with simple chemical systems, although rarely stated, is equally dramatic. One of the main objectives of mechanics applied to chemical systems is to predict how an amount of energy, transferred to a closed system, gets be distributed among individual molecules.