Ozone (O3) is a relatively unstable and very reactive compound formed by the action of electricity on oxygen. It is familiar as the source of the distinctive odor associated with thunderstorms, where it is formed by lightning strikes. It is also formed in the atmosphere by the action of chemical pollutants impacted by ultraviolet radiation from the sun. Because it is toxic, it is used as an indicator of air quality. Higher up in the atmosphere, it helps to shield life on earth from excessive ult…