In the formula: The nonmetal has fixed oxidation
number: halogens -1, chalcogens -2, group of N -3, group of C -4, and the
oxidation number of the metal can be deduced by knowing that the compound is
neutral. If it is always the same, we must know it and it is not necessary to
How to determine the oxidation number of the metal?
1. Multiply the oxidation number of the nonmetal by its
subscript. Change the sign of the result.
2. Divide this result by the subscript of the metal. This is the value of the
oxidation number of the metal, and of the Roman number that you must use.