# How do you assign the oxidation number to HCl?

Jun 24, 2016

For a neutral molecule, the sum of the individual oxidation numbers must sum to ZERO.

#### Explanation:

Hydrogen has a $+ I$ oxidation number, and chlorine a $- I$ oxidation number in the neutral gas $H C l$.

Perchloric acid, $H C l {O}_{4}$, contains oxygen atoms that have a $- I I$ oxidation number. What is the oxidation number of chlorine here?