Write the rules for assigning oxidation number .
(1) All atoms in the elemental or molecular state have 'zero'oxidation state.
(2)Elements of group $$ I $$ and $$ II $$ in the periodic table always have $$ '+1'$$ and $$ '+2' $$ oxidation states respectively.
(3). Hydrogen $$ '+1'$$ oxidation state in all its compounds expect metal hydrides where it is $$ '-1'$$
(4) Oxygen has been assigned an oxidation number of $$ '-2' $$ in all its compounds except peroxides and oxygen fluoride. In peroxide it is $$ '-1'$$and in oxygen fluoride it is $$ '+2'$$.
(5) Halogens generally have $$ '-1'$$ oxidation state. Except for fluorine, other halogens may have positive oxidation states in their oxides and inter halogen compounds (Flurione always has $$ '-1'$$ state).
(6) The algebraic sum of oxidation numbers of all the elements in a compound is zero and that in ion is equal to the net charge on the ion.