The book systematically outlines non-relativistic quantum mechanics. The author analyzes in detail the physical content and examines in detail the mathematical apparatus of one of the most important sections of modern natural science - atomic theory. The book is written in a simple and intelligible language. All this makes the book very useful for the reader who is beginning to get acquainted with quantum mechanics. Designed for engineers and scientists, as well as students and graduate students specializing in physics and physical chemistry.