The monograph is written at the modern scientific level, taking into account the latest achievements in the field of chemical bonding theory. It quite simply and informally sets out the necessary minimum of information on the basics of quantum chemistry, methods of molecular orbitals and valence bonds. Various types of chemical bonds, the structure of some simple inorganic compounds are considered, much attention is paid to the theory of bonds in complex compounds. The monograph is intended for a wide range of chemists interested in the current state of valence theory. It will be useful for teachers and students of chemical universities and universities.