Write any theee rules assigning for the oxidation number ?

Explanation

`ast` The oxidation state of a free elements (i.e., in its uncombined state) is zero.
Example : each atom in `H_2CI_2,Na,S_8` have the oxidation number of zero.
`ast` For a monatomic ion, the oxidation state is equal to the net charge on the ion.
Example : The oxidation number of sodium in `Na^(+)` is `+1`.
The oxidation number of chlorine in `CI^(-)` is `-1`.
`ast` The algebric sum of oxidation states of all atoms in a molecule is equal to zero, while in ions, it is equal to the net charge on the ion.