# What is the oxidation number of oxygen in hydrogen peroxide?

In hydrogen peroxide, the oxidation number of each oxygen is $- I$.
With $H - O - O - H$, we break a $H - O$ bond, and get ${H}^{+}$ and ""^(-)O. However, if we break an $O - O$ bond the 2 electrons in the $O - O$ bond are SHARED between the oxygen atoms, to give $2 \times \cdot {O}^{-}$; i.e. the oxygen atoms necessarily have the same electronegativity.