# What is superoxide? Please explain

Jun 9, 2018

An old name for the ${O}_{2}^{-}$ ion...

#### Explanation:

This is copied from an old answer, and attempts to explain the difference between $\text{oxides}$, $\text{peroxides}$, and $\text{superoxides}$....

Most oxygen containing compounds are OXIDES....i.e. they feature oxygen in its stable $\stackrel{- I I}{O}$ oxidation state. Water, certainly features oxygen with this designation....

Now hydrogen peroxide is $H O - O H$, and it clearly contains an $O - O$ bond. Because our definition of oxidation number is $\text{the charge left on the central atom when all the bonding pairs}$ $\text{of electrons are BROKEN, with the charge assigned}$ $\text{to the most electronegative atom,}$ this exercise results in the sharing of the electrons (because the oxygen atoms have equal electronegativity):

i.e. $H O - O H \rightarrow 2 \times \dot{O} H$

($\dot{O} H$ is the so-called hydroperoxyl radical). The oxygen in hydrogen peroxide has a formal oxidation of $- I$.

And when we write peroxide salts, i.e. sodium peroxide, we use a formula of $N {a}_{2} {O}_{2}$; i.e. a salt of ""^(-)O-O^-.

And for $\text{superoxides}$, to continue the formalism, we write ${O}_{2}^{-}$, that is a mixed oxidation state dioxide of ${O}^{0}$ and ${O}^{-}$, to give an average oxidation number of ${O}^{- \frac{1}{2}}$. In very old literature, this goes by the label $\text{hyperoxide}$.