Chemistry students need a basic understanding of quantum theory and its applications to atomic and molecularstructure and spectroscopy. This book develops the basic concepts needed as background, and discusses atomic structure but not molecular applications. The first two chapters are concerned with the basic ideas and problems of wave-particle duality, the nature of wavefunction, and its statistical interpretation. Chapter 3 discusses some important applications of Schrodinger’s equation to chemically relevant situations. Chapters 4 and 5 deal respectively with the hydrogen atom, and with the structure of many electron atoms and the periodic table of elements. The emphasis throughout is on the physical concepts and their concrete application. The required background in mathematics is elementary calculus and the properties of trigonometric and exponential functions, but not complex numbers. Necessary concepts of classical physics are developed as required.