Assigning Oxidation States – Rules

ASSIGNMENT OF OXIDATION STATES: RULES

(i) For anions and cations, the oxidation number is equal to the charge on the ion.

(ii) The oxidation number of a free element is zero.

(iii) Any element, when not combined with atoms of a different element, has an oxidation number of zero (e.g. O₂, P₄, S₈).

(iv) For polar covalent molecules or ions, we assign to the MORE ELECTRONEGATIVE atom of a bond the total
possession of the electron pairs in the bond.

Therefore:

F always has an oxidation state of -I

O generally has an oxidation state of -II

H usually has an oxidation state of +I.