Ozone (O3) is a substance whose molecule is composed of three oxygen atoms, formed when the two atoms that make up oxygen gas dissociate. Each released oxygen atom bonds with another oxygen molecule (O2), forming ozone molecules (O3).

Ozone has industrial uses as a precursor in the synthesis of some organic compounds, but mainly as a disinfectant, purifier, and cleanser of mineral waters. Its main property is that it is a very strong oxidant. It is also known for its important role in the atmosphere by filtering the UV radiation that reaches the Earth.

When oxygen in the air is subjected to a high-energy pulse, such as lightning, the double O=O bond of oxygen breaks, releasing two oxygen atoms which then recombine with other oxygen molecules. These recombined molecules contain three oxygen atoms instead of two, resulting in ozone.