This book presents quantum mechanics through a systematic progression from classical atomic models to modern quantum theory. Beginning with foundational concepts, the text develops Schrödinger's equation and its applications to fundamental quantum systems. Mathematical rigor is balanced with physical interpretation throughout. Detailed derivations of quantum mechanical principlesComprehensive treatment of particle systems, rigid rotators, and harmonic oscillatorsIn-depth analysis of hydrogen atom wavefunctions and multi-electron systemsApplications to rotational, vibrational, and electronic spectroscopyComparative presentation of Valence Bond and Molecular Orbital theoriesIdeal for advanced undergraduate and graduate students in chemistry and physics. This title has been co-published with Manakin Press. Taylor & Francis does not sell or distribute the print edition in India, Pakistan, Nepal, Bhutan, Sri Lanka and Bangladesh.