Ozone

Allotropic form of oxygen containing three atoms in the molecule. The stratosphere ozone layer, which is a concentration of ozone molecules located at 10 to 50 kilometres above sea level, is in a state of dynamic equilibrium. Oxygen molecules absorb ultraviolet (UV) light to form ozone which, in turn, decomposes back to oxygen. These processes absorb most of the ultraviolet light from the sun, shielding life from the harmful effects of UV radiation. Ozone is normally present at ground level in low concentrations. In cities where high level of air pollutants is present, the action of the sun’s ultraviolet light can, through a complex series of reactions, produces harmful concentrations of the ground level ozone. The resulting air pollution is known as photochemical smog.

Symbol

O₃

See also: Oxygen.