# What is the oxidation number of oxygen in potassium oxide, K_2O?

Jan 2, 2017

We have ${O}^{2 -}$, and thus $O \left(- I I\right)$.

#### Explanation:

Oxidation number is the charge left on the atom of interest, when all the bonding electrons are removed with the charge devolved to the more electronegative atom.

We have the ionic salt, ${K}_{2} O$. Clearly, oxygen is more electronegative than potassium, and so we have $2 \times {K}^{+} + {O}^{2 -}$.

The oxidation number of $O$ in oxide anion is thus $- I I$.

What about in $\text{potassium peroxide}$, ${K}_{2} {O}_{2}$. We still have ${K}^{+}$. What's the oxidation state of oxygen?