Molecular Quantum Mechanics shows how the subject of quantum mechanics embraces the behaviour of all known forms of matter, including the atoms and molecules from which we, and all living organisms, are composed. The book leads us through this subject, exploring the fundamental physical principles that explain how all matter behaves. The text takes us from the foundations of quantum mechanics, through quantum models of atomic, molecular, and electronic structure, and on to discussions of spectroscopy, and the electronic and magnetic properties of molecules.