1. The number of oxidation states increases with the number of electrons available, and it decreases as the number of paired electrons increases.
2. Hence, the first and last elements show less number of oxidation states and the middle elements with more number of oxidation states.
3. For example, the first element Sc has only one oxidation state +3, the middle element Mn has six different oxidation states from +2 to +7. The last element Cu shows +1 and +2 oxidation states only.
