d - block elements exhibit greater number of oxidation states than f - block elements. Explain.

Explanation

In case of d - block elements, the ns and (n - 1)d electrons take part in bond formation. Hence, d - block elements show variable oxidation states. In case of f - block elements, due to decrease in the screening effect of f - subshell, the influence of nucleus on the outer electrons increases and hence, these electrons are not involved in bonding. Moreover, the f - electrons are located in the anti - penultimate (n - 2) - orbitals and are greatly attracted by the nucleus. So f - electrons are reluctant to take part in bonding. Therefore, the f - block elements do not exhibit greater number of oxidation states.