How to find the oxidation number of S in Na2SO3.
If you want to calculate oxidation numbers of elements in the chemical compound, enter it's formula and click 'Calculate'.
The charge of an atom is the oxidation state.The oxidation state is synonymous with the oxidation number.It is easy to determine oxidation numbers from the Lewis structure.The oxidation number of each atom can be calculated by subtracting the sum of lone pairs and electrons it gains from bonds.Homonuclear bonds are always divided equally.
When dealing with organic compounds and formulas with multiple atoms of the same element, it's easier to work with molecular formulas and average oxidation numbers.Anything that doesn't change before the first C-C bond is replaced with the abbreviation R can be written in such a way.R cannot be hydrogen.The R group doesn't change the oxidation number of the carbon atom it's attached to because the electrons between two carbon atoms are evenly spread.There are examples of usage on the Divide the redox reaction page.