TS EAMCET 20-July-2022 Shift 2 Solved Paper

Mo atomic number is 42 , so the ground state electronic configuration can be written as
‌

[Kr]

↓ 36

4d55s1
Exchange energy is energy liberated when 2 or more electrons with similar spin exchange their positions in the degenerate orbitals.
More the number of unpaired electrons, more will be the exchange energy.
As both 4d and 5s-orbitals in Mo are exactly half-filled and it has 5 unpaired electrons in d-orbitals which are degenerate.
∴ Will have highest exchange energy amongst the second row elements which might have either less than 5 electrons in d-orbitals or more than 5 electrons in d-orbitals.
Hence, both (A) and (R) is true but (R) is not the correct explanation for (A). The highest exchange energy is due to half-filled electronic configuration.