The goal of the course is to provide students with a fundamental understanding of the quantum chemical description of atoms and molecules. Particular emphasis is placed on the understanding of chemical structure elucidation and bonding together with the theoretical basis for quantum theory. The course provides the first practical experience and the future starting point for solving structural and dynamical problems in chemistry by applying spectroscopic experiments and quantum chemical calculations. Furthermore, the course provides the fundamental quantum chemical background required for further courses in molecular modelling, molecular spectroscopy, inorganic chemistry and physical organic chemistry.