* Hydrogen's Oxidation State: Hydrogen usually has an oxidation state of +1, except when bonded to metals.

* Neutral Molecule: The overall charge of H₂O₂ is zero.

* Balancing the Charges: To achieve a neutral molecule, the two oxygen atoms must have a combined oxidation state of -2 (to balance the +2 from the two hydrogen atoms).

* Equal Distribution: Since both oxygen atoms are in the same environment, they each have an oxidation state of -1.

Therefore, the oxidation state of oxygen in H₂O₂ is -1.