We have attempted to improve and update this text while retaining the features that make it unique, namely, an emphasis on physical understanding, and the ability to estimate, evaluate, and predict results without blind reliance on computers, while still maintaining rigorous connection to the mathematical basis for quantum chemistry. We have inserted intomost chapters examples that allowimportant points to be emphasized, clarified, or extended. This has enabled us to keep intact most of the conceptual development familiar to past users. In addition, many of the chapters now include multiple choice questions that students are invited to solve in their heads. This is not because we think that instructors.
