Homonym: O3 (Ozone)
O3, commonly known as ozone, is a molecule composed of three oxygen atoms. It is found naturally in the Earth's atmosphere, primarily in the stratosphere, where it forms the ozone layer. This layer plays a crucial role in protecting life on Earth by absorbing the majority of the sun's harmful ultraviolet (UV) radiation.
Ozone can also be found at ground level, where it is a significant component of smog. Ground-level ozone is created when sunlight reacts with pollutants from vehicles and industrial sources. While it can help protect against UV radiation in the upper atmosphere, at ground level, it can be harmful to human health and the environment.