Question

Given below are two statements, one is marked as Assertion and other is marked as Reason.

Assertion (A): Crystal field splitting is less in tetrahedral complexes as compared to octahedral complexes and can be related as $\triangle_t = \frac{4}{9}\triangle_o$. (If ligand and metal ion are same)

Reason (R): In case of octahedral coordination entities, the energy of two $e_g$ orbitals will increase by $(\frac{3}{5})\triangle_o$ and that of three $t_{2g}$ orbitals will decrease by $(\frac{2}{5})\triangle_o$.

In the light of the above statements, choose the correct answer from the options given below.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Assertion is incorrect but Reason is correct.

Answer 1

Answer: (B)

B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

Answer 2

Assertion (A) is correct because the crystal field splitting energy in tetrahedral complexes ($\triangle_t$) is generally less than in octahedral complexes ($\triangle_o$), and the relationship $\triangle_t = \frac{4}{9}\triangle_o$ is a standard approximation. Reason (R) is also correct, as it accurately describes the energy distribution of d-orbitals in an octahedral complex relative to the barycenter ($\triangle_o$). However, Reason (R) explains the energy levels within an octahedral field and does not provide the underlying cause for the difference in splitting magnitudes between tetrahedral and octahedral complexes or the origin of the $\frac{4}{9}$ factor. Thus, Reason (R) is not the correct explanation for Assertion (A).