Question

What is the oxidation state of chlorine in `ClO_2`?

Answer 1

The oxidation number of Cl in ClO₂ is +4.

Explanation:

You can learn how to calculate oxidation states at

http://socratic.org/questions/how-do-you-find-the-oxidation-number-of-an-element

For your problem, the important rules are

1. Oxygen usually has an oxidation number of -2. Exceptions include molecules and polyatomic ions that contain O-O bonds, such as O2, O3, H2O2, and the O22- ion.

2. The sum of the oxidation numbers in a neutral compound is zero.

Thus, in ClO₂, the oxidation number of O is -2 (Rule 1)

For two O atoms, the total oxidation number is -4.

So the oxidation number of Cl must be +4. This makes the sum of all the oxidation numbers equal to zero (Rule 2).