The Quantum Mechanics of Matter shows how quantum mechanical methods are used to explain the behaviour of matter, from the scale of nuclei and atoms to molecules and solids. The hydrogen atom is discussed in detail, as well as hydrogen-like systems such as charmonium. The useful technique of perturbation theory is developed to obtain approximate results in cases where exact calculations become difficult. The book goes on to discuss multi-electron atoms and the Periodic Table, molecular binding and the behaviour of electrons in the energy bands of metals, insulators and semiconductors. Finally, the book considers the interaction of matter with light. You will see how quantum mechanics can predict the lifetimes of atomic states and the brightness of spectral lines.