This unique book and accompanying software provides concise, exhaustive, and clear descriptions of terms, notations, concepts, methods, laws, and techniques that are necessary for engineers and researchers dealing with physical and chemical processes in gas and plasma dynamics. It reflects the state of the art of physico-chemical gas dynamics and is designed to serve the modern needs of the related areas of science and technology. This first volume of a two-volume set treats the dynamics of elementary processes (cross section and rate coefficients of chemical reactions, ionisation and recombination processes, and inter- and intramolecular energy transfer). Volume II will discuss complex physical and chemical kinetics in gases and plasmas.