NEET2026ChemistryChapterActual
The third ionization enthalpy of manganese ( Z=25 ) is exceptionally high, whereas that of iron ( Z=26 ) is comparatively lower. This contrast is best explained by the respective electronic configuration changes during the removal of the third electron, which correspond to the transitions:
Options
- Ad ^5 d ^4 in Mn ²⁺ and d ^6 d ^5 in Fe ²⁺
- Bd ^5 d ^6 in Mn ²⁺ and d ^4 d ^5 in Fe ²⁺
- Cd ^4 d ^3 in Mn ²⁺ and d ^5 d ^4 in Fe ²⁺
- Dd ^6 d ^5 in Mn ²⁺ and d ^5 d ^4 in Fe ²⁺
Correct answer
A. d ^5 d ^4 in Mn ²⁺ and d ^6 d ^5 in Fe ²⁺
Step-by-step solution
The atomic number of manganese ( Mn ) is 25 . Its ground state electronic configuration is [ Ar ] 3 d ^5 4 s ^2 . During the removal of the first two electrons to form Mn ²⁺ , the 4 s electrons are removed, resulting in the configuration [ Ar ] 3 d ^5 . The third ionization enthalpy involves the removal of an electron from Mn ²⁺ to form Mn ³⁺ . This corresponds to the transition 3 d ^5 3 d ^4 . Since the 3 d ^5 configuration is exactly half-filled and exceptionally stable, removing an electron from it requires a ve