Textbook in PDF format Useful introductory course and reference covers origins of quantum theory, Schrödinger wave equation, quantum mechanics of simple systems, electron spin and many-electron systems, the quantum states of atoms, the Hartree-Fock self-consistent field method, the electronic structure of molecules, semiempirical molecular orbital methods, more. Supplemented by 7 appendixes. Origins of the Quantum Theory The Schrodinger Wave Equation The Quantum Mechanics of Some Simple Systems Quantum Theory of Angular Momentum: The Rigid Rotator The Hydrogen Atom Approximate Solutions to the Schrödinger Equation Electron Spin and Many-Electron Systems The Quantum States of Atoms The Algebra of Many-Electron Calculations The Hartree-Fock Self-Consistent Field Method Introduction to Molecular Structure The Electronic Structure of Linear Molecules The Electronic Structure of Nonlinear Molecules Semiempirical Molecular Orbital Methods I: Pi Electron Systems Semiempirical Molecular Orbital Methods II: All Valence-Electron Systems Electronic Transitions in Molecules Summary of the MO-LCAO Approximation The Hydrogen Molecule Ion, image Scaling and the Virial Theorem for Diatomic Molecules The Hydrogen Molecule (Dihydrogen) The Aufbau Principle for Homonuclear Diatomic Molecules Heteronuclear Diatomic Molecules Linear Polyatomic Molecules Molecular Configuration-Interaction Calculations Natural Orbital Analysis of Molecular Wavefunctions Molecular Perturbation Calculations The Electronic Structure of Nonlinear Molecules  Semiempirical Molecular Orbital Methods I: Pi Electron Systems  Semiempirical Molecular Orbital Methods II: All Valence-Electron Systems Appendices Values of Physical Constants Electrostatic and Electromagnetic Units Evaluation of Some Simple Helium Atom Integrals Vector and Operator Algebra Elements of Matrix Algebra Molecular Symmetry Character Tables for Some Common Molecular Point Groups