# What is the oxidation number for oxygen?

Mar 5, 2014

In its compounds, Oxygen usually has an oxidation number of -2 , ${O}^{-} 2$

Oxygen has an electron configuration of

$1 {s}^{2} 2 {s}^{2} 2 {p}^{4}$

To complete its valence shell and satisfy the octet rule, the oxygen atom will take on two electrons and become ${O}^{-} 2$.

In peroxides, such as ${\text{H"_2"O}}_{2}$, ${\text{Na"_2"O}}_{2}$, and $\text{BaO"_2}$, each oxygen atom has an oxidation number of -1.

In the free element, $\text{O"_2}$, each oxygen atom has an oxidation number of zero.

I hope this was helpful.

SMARTERTEACHER