The ten most common compounds in the earth's crust are all oxides. Most of the lanthanides exist in nature as their oxides. Even the noble gases are not totally immune to forming oxides. There are two allotropes of oxygen. The latter is known as ozone .
Ozone is a very strong oxidizing agent .
It is useful as a disinfectant and bleaching agent. It is also used in the treatment of sewage and the manufacture of chemicals. Ozone occurs naturally in the earth's upper atmosphere where it serves as an effective shield against harmful radiation from teh sun. Commercial amounts are prepared by passing O 2 through an electric spark. The pungent odor often detected around electrical equipment is often that of ozone.