This unique text provides a non-mathematical and highly visual account of the concepts of quantum mechanics widely encountered in chemistry and related disciplines. Alphabetically organized entries describe the physical significance of each topic precisely and simply. Each entry is extensively cross-referenced and ends with a guide to sources of further information. Richly illustrated with drawings and tables, this exciting work is completely rewritten. All topics have been brought up to date, and there are many more illustrations and numerous new entries, along with a revised bibliography. The work continues the tradition of the first edition, which quickly established itself among students and teachers alike as a rich source of clear, concise explanations of quantum concepts. In addition to its value for students and instructors in physical and theoretical chemistry, practicing scientists will find the succinct overviews very useful. The book is also accessible to interested general readers.