What is the oxidation number for arsenic in the product of the following reaction? As + Cl2 → AsCl3

+3

Explanation:

The oxidation number of a specie is the charge that it appears to have as determined by some arbitrary rules.

If we look at the reaction, we will notice that arsenic is more electro positive than chlorine so it is likely to function as the reducing agent in the reaction, loosing three electrons to have an oxidation number of +3 in the product.