MOLECULES and the Chemical Bond is about understanding Schrodinger's equation, for chemical systems. In his famous Lectures on Physics, Richard Feynman quotes Paul Dirac on what it means to understand an equation. "I understand what an equation means," said Dirac, "if I have a way of figuring out the characteristics of its solutions without actually solving it." That hits the nail on the head! It's precisely what Conceptual Valence Bond Theory does for Schrodinger's equation. A "physical understanding" of an equation, adds Feynman, "is a completely unmathematical, imprecise, and inexact thing, but absolutely necessary for a physicist." It unfolds in MCB in two stages, described by Newton as a stage of "Analysis" (a union of observations and inductions) and a stage of "Synthesis" (use of inductions, accepted as first principles, to explain observations). The book's chief vehicle for creating an intuitive understanding of solutions of Schrodinger's equation is the world's largest - and to the author's knowledge, virtually only - library of line drawings of exclusive orbital models of chemical species' electron density profiles.
Electron domain model of "calcium electride", Ca+2e2-2 (and isoelectronic potassium hydride, K+H-). Red: domains of outer electrons of one spin of Ca+2 (or K+). White: domains of outer electrons of the opposite spin. Pink: domains of spin-paired bonding "electride ions", e2-2 (or, protonated, hydride ions, H-). By focussing attention on fundamental physical principles and by avoiding use of atomic orbitals and, thereby, mathematical complexities associated with Schrodinger's equation (the only source of atomic orbitals), the book's essays provide a scientifically sound, student-friendly introduction to modern valence theory. Repetition of fundamental ideas, here and there, is intended to make individual essays understandable and interesting, each by itself, so that readers may examine them in any order, in leisurely walks, so to speak, in the big garden that is valence theory, picking bouquets to their liking.
