In this post, we will determine the oxidation numbers in hydrogen peroxide, H2O2.

To determine the oxidation number of an atom(s) in a molecule or an ion, start with the known oxidation numbers and the rules summarized below:



Keep in mind that the summary is zero for neutral molecules and is equal to the charge for ions.

For H2O2 the element with a standard oxidation state is hydrogen which is +1, and we need to determine the oxidation state of the oxygen. 

Rule 6 – The oxidation of hydrogen is +1:

Assign x for the oxidation state of O and set up an equation:


2(+1) + 2x = 0,  x = -1

This is an unusual oxidation number of oxygen in a molecule, and the reason is that the two oxygens are connected, so they each pull the electron density only from one hydrogen atom:

We discussed the Lewsis structure and hybridization of H2O2 in a separate article which you can find here


Further Reading


More examples of the oxidation state in this multiple-choice quiz:


Oxidation State and Redox Reactions Quiz


Reactions in Aqueous Solutions Quiz


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