The understanding in science implies insights from several different points of view. Alternative modern outlooks on electronic structure of atoms and molecules, all rooted in quantum mechanics, are presented in a single text. Together these complementary perspectives provide a deeper understanding of the localization of electrons and bonds, the origins of chemical interaction and reactivity behavior, the interaction between the geometric and electronic structure of molecules, etc. In the opening two parts the basic principles and techniques of the contemporary computational and conceptual quantum chemistry are presented, within both the wave-function and electron-density theories. This background material is followed by a discussion of chemical concepts, including stages of the bond-formation processes, chemical valence and bond-multiplicity indices, the hardness/softness descriptors of molecules and reactants, and general chemical reactivity/stability principles. The insights from Information Theory, the basic elements of which are briefly introduced, including the entropic origins and Orbital Communication Theory of the chemical bond, are the subject of Part IV. The importance of the non-additive (interference) information tools in exploring patterns of chemical bonds and their covalent and ionic components will be emphasized.

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Mathematical apparatus
Basic concepts and axioms
Hydrogen-like atom
Approximating N-electron Schrödinger equation
Wave function methods
Density-Functional Theory
Bonded subsystems and chemical bonds
Concepts for chemical reactivity
Adiabatic coupling between electronic and geometric structures
Elements of information theory
Schrödinger equation as information principle
Electron probabilities as carriers of information in molecules
Bonded atoms from information theory
Molecular communication systems
Orbital communication theory of the chemical bond
"Thermodynamic" description.