The oxidation state of an atom or ion is the number of electrons that are taken away or given to it. Positive oxidation states are electrons taken away and negative oxidation states are electrons given. When tin dissolves in sulfuric acid to make tin(II) sulfate, the tin loses two electrons and becomes a Sn2+ ion, which is tin in its +2 oxidation state. The hydrogen ion (H+) gains an electron from the tin, changing the oxidation state from +1 to 0. All elements have an oxidation state of 0.