A Textbook of Physical Chemistry Fifth Edition is directed towards undergraduate science, engineering and pharmacy students. Most of the chapters have been revised to keep up with recent discoveries. Thus, chapters on Atomic Structure, Chemical Bonding, Photochemistry, Physical Properties and Chemical constitution have been revised and changes have been made in other chapters also.Both the traditional cgs/esu and the newer SI systems of units have been used identically. This is so because in spite of wider acceptance of the SI units, the cgs units continue to be used in most chemical literature.The book emphasizes fundamental rather than excessive details and develops the topics from the first principles. It contains a considerable number of worked-out examples, exposing the students to practical applications of equations and helping them comprehend many different physiochemical quantities.