A superoxide, also known by the obsolete name hyperoxide, is a compound that contains the superoxide anion with the chemical formula O2−. The systematic name of the anion is dioxide(1−). Superoxide anion is particularly important as the product of the one-electron reduction of dioxygen O2, which occurs widely in nature. With one unpaired electron, the superoxide ion is a free radical, and, like dioxygen, it is paramagnetic.
Read more about Superoxide: Properties, Biology, Assay in Biological Systems