This book describes atomic orbitals at a level suitable for undergraduates in chemistry. The mathematical treatment is brought to life by many illustrations rendered from mathematical functions (no artists‘ impressions), including three-dimensional plots of angular functions, showing orbital phase, and contour plots of the wavefunctions that result from orbital hybridisation.Orbitals extends the key fundamental quantum properties to many-electron atoms, linear combinations of atomic orbitals, simple molecules, delocalised systems and atomic spectroscopy. By focusing on simple model systems, use of analogies and avoiding group theory the results are obtained from initial postulates without the need for sophisticated mathematics.