A: The degeneracy of d-orbitals is lost under strong field ligand
R: The degeneracy of d-orbitals does not get lost under weak field ligand

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. ) If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze the assertion (A) and the reason (R) provided.

### Step 1: Understand the Assertion (A)
The assertion states that "The degeneracy of d-orbitals is lost under strong field ligands."
- In coordination chemistry, when a metal ion is surrounded by ligands, the five d-orbitals split into two energy levels due to the electrostatic interactions between the ligands and the d-electrons.
- Strong field ligands cause a significant splitting of these orbitals, resulting in the loss of degeneracy (the condition where orbitals have the same energy).
- Therefore, this assertion is **true**.

### Step 2: Understand the Reason (R)
The reason states that "The degeneracy of d-orbitals does not get lost under weak field ligands."
- Weak field ligands cause less splitting of the d-orbitals compared to strong field ligands.
- However, it is important to note that even weak field ligands do cause some splitting of the d-orbitals, but the extent of splitting is less than that caused by strong field ligands.
- Therefore, while the reason suggests that degeneracy is maintained under weak field ligands, it is misleading because there is still some splitting, albeit less significant. Hence, this reason is **not correct**.

### Step 3: Conclusion
- The assertion (A) is true.
- The reason (R) is false because it incorrectly implies that there is no splitting under weak field ligands.

### Final Answer
- The assertion is true, but the reason is not a correct explanation of the assertion.