# What are the oxidation numbers in the compound H2O2?

Jul 2, 2014

The oxidation number of $\text{H}$ is +1. The oxidation number of $\text{O}$ is -1.

#### Explanation:

You assign oxidation numbers to the elements in a compound by using the Rules for Oxidation Numbers.

The important rules for this problem are:

1. The oxidation number of $\text{H}$ is +1, but it is -1 in when combined with less electronegative elements.

2. The oxidation number of $\text{O}$ in compounds is usually -2, but it is -1 in peroxides.

3. The sum of the oxidation numbers of all the atoms in a neutral compound is 0.

The oxidation number of $\text{H}$ is +1 (Rule 1).

If you know that ${\text{H"_2"O}}_{2}$ is hydrogen peroxide, you can immediately assign oxygen the ON = -1.

If you don't know that ${\text{H"_2"O}}_{2}$ is hydrogen peroxide, you can use Rule 3.

The oxidation number of $\text{H}$ is +1. For two $\text{H}$ atoms, the sum is +2.

Since ${\text{H"_2"O}}_{2}$ has no charge, the total oxidation number of the two $\text{O}$ atoms must be -2.

The oxidation number of one oxygen atom must be -1.