Theoretical chemistry involves explaining chemical phenomenon using natural
laws. The primary tool of theoretical chemistry is quantum chemistry, and the field
may be divided into electronic structure calculations, reaction dynamics and statistical
mechanics. These three all play a role in addressing an issue of primary concern:
understanding photochemical reaction rates at the various conditions found
in the atmosphere. Atmospheric science includes both atmospheric chemistry and
atmospheric physics, meteorology, climatology and the study of extraterrestrial
atmospheres.