Question

What is the oxidation state of chlorine in NaClO2?

Answer 1

+3

`NaClO_2` has the proper name sodium chlorate(III). The (III) is the oxidation number of chlorine in the chlorate ion here.

To work thus out you need to know that sodium in compounds always has an oxidation number of +1 ( which you'd expect as it is in Group 1), and oxygen has an oxidation number of -2 in its compounds (except for peroxides).

You then use the rule that the sum of the oxidation numbers in a compound must add to zero, and Na (+1) + Cl (+3) + O (-2) + O (-2) =0