Ozone

Ozone (O₃) is a substance consisting of molecules of three bound oxygen atoms. At standard temperature and pressure it is a blue gas. It forms a dark blue liquid below -112 C and a dark blue solid below -193 C.

It is a highly corrosive and poisonous substance and a common pollutant. It has a sharp, pungent odour. It's present in low concentrations throughout the Earth's atmosphere. It is formed naturally from O₂ by electrical discharges, e.g., lightning?, and by action of high energy electromagnetic radiation.

The highest levels of ozone in the atmosphere are in the stratosphere?, in a region also known as the [ozone layer]?. Here it filters out much ultraviolet light from the Sun that would be harmful to most forms of life. See also ozone hole.

Ozone was discovered by [Christian Friedrich Schonbein]? in 1840.