Provides an introduction to the structure and composition of the atmosphere. It gives an overview of the quantitative description of atmospheric gas abundances and introduces the fundamental concepts of atmospheric chemistry, including photochemistry, reaction kinetics, steady state, gas emissions, etc. The central chemical processes controlling atmospheric composition are described for specific trace gases and trace gas families, such as tropospheric and stratospheric ozone Ozone ()stratospheric, free radicals, andNitrogen Oxides () oxides of nitrogenOxides of nitrogen, sulfur, and halogens. Current environmental challenges, including urban smogSmog and the Antarctic ozone hole Ozone ()hole, are discussed.