In this 1986 book, Dr Matthews emphasises the fundamental ideas of quantum theory as they relate to mainstream areas of quantum theory such as bonding and spectroscopy; elementary ideas on the use of symmetry are also included. No prior knowledge of quantum theory is assumed, and considerable help is given in understanding the mathematics that is involved. Much of this mathematics is integrated into the text, but the more intricate portions are to be found in separate boxes; these can be left on a first reading and returned to later. There are also questions and problems at the end of nearly every section, and these are designed to test the student's understanding of the text and to give fresh insights into the work; full answers are provided.