Chemical composition of the atmosphere. Physical and chemical transformations. Chemical kinetics. Photochemical reactions. Sources, sinks and transport. Tropospheric chemistry, tropospheric O3, free radicals, Nitrogen oxides, CO, Hydrocarbons. Heterogeneous reactions, SO2 oxidation, acid deposition. Stratospheric chemistry, stratospheric O3, catalytical cycles (HOx, NOx, ClOx), The role of anthropogenic emissions of CFCs. The ozone hole chemistry.