This book explores chemical bonds, their intrinsic energies, and the corresponding dissociation energies which are relevant in reactivity problems. It offers the first book on conceptual quantum chemistry, a key area for understanding chemical principles and predicting chemical properties. It presents NBO mathematical algorithms embedded in a well-tested and widely used computer program (currently, NBO 5.9). While encouraging a "look under the hood" (Appendix A), this book mainly enables students to gain proficiency in using the NBO program to re-express complex wavefunctions in terms of intuitive chemical concepts and orbital imagery.
Keywords: Computational Chemistry & Molecular Modeling, many-electron molecular wavefunction, Natural Bond Orbitals, NBO, electronic structure software, chemical bonding, electronic structure calculations, conceptual quantum chemistry, Schr??dinger's equation, system wavefunction, nanoscience, computational biology, computational chemistry