In which of the following configuration will there be the possibillity of both para and diamagnetism depending on the nature of the ligands ?

Options

A. `d^(3)`
B. `d^(7)`
C. `d^(6)`
D. `d^(5)`

Answer

To determine which electronic configuration allows for both paramagnetism and diamagnetism depending on the nature of the ligands, we need to analyze the electron configurations of different d-block systems (d3, d5, d6, and d7) under strong and weak field ligands.

### Step-by-Step Solution:

1. **Understanding Ligand Field Theory**:
- In coordination compounds, ligands can be classified as strong field or weak field.
- Strong field ligands cause electron pairing in the lower energy orbitals (t2g) before filling the higher energy orbitals (eg).
- Weak field ligands allow electrons to occupy higher energy orbitals (eg) before pairing occurs in the lower energy orbitals (t2g).

2. **Analyzing d3 Configuration**:
- For d3:
- Strong field: 3 electrons will fill the t2g orbitals (no unpaired electrons, diamagnetic).
- Weak field: Same filling (3 electrons in t2g), still no unpaired electrons (diamagnetic).
- Conclusion: d3 does not exhibit both behaviors.

3. **Analyzing d5 Configuration**:
- For d5:
- Strong field: 5 electrons will fill t2g and one electron will be in eg (4 unpaired electrons, paramagnetic).
- Weak field: 5 electrons will fill t2g and eg (5 unpaired electrons, paramagnetic).
- Conclusion: d5 does not exhibit both behaviors.

4. **Analyzing d6 Configuration**:
- For d6:
- Strong field: 6 electrons will fill t2g completely (3 pairs, no unpaired electrons, diamagnetic).
- Weak field: 6 electrons will fill t2g (3 pairs) and one electron in eg (1 unpaired electron, paramagnetic).
- Conclusion: d6 exhibits both behaviors depending on the ligand strength.

5. **Analyzing d7 Configuration**:
- For d7:
- Strong field: 7 electrons will fill t2g and one in eg (1 unpaired electron, paramagnetic).
- Weak field: 7 electrons will fill t2g and eg (3 unpaired electrons, paramagnetic).
- Conclusion: d7 does not exhibit both behaviors.

### Final Answer:
The configuration that allows for both paramagnetism and diamagnetism depending on the nature of the ligands is **d6**.