- The oxidation number of all elements in the free state is zero e.g. Na, CL2 etc.
- The oxidation number of a simple ion has the same sign as the change of the Ion.
EXAMPLE:
Calculate the oxidation of carbon In CaCO2
Solution
Ca = +2, O = 2
∴Ca2+; O-2
∴2 x 1 +x – 2×3 = 0
2 +x – 6 = 0
x – 4 = 0
x = 4
The oxidation number of carbon In CaCO3 is 4.