Which of the following shell form an outer octahedral complex

Options

A. `d^4`( low spin )
B. `d^8` (high spin)
C. `d^6` (low spin)
D. None of these

Explanation

To determine which of the given shells can form an outer octahedral complex, we need to understand the concept of coordination compounds and the geometry associated with octahedral complexes.

### Step-by-Step Solution:

1. **Understand Octahedral Geometry**:
- An octahedral complex is formed when a central metal atom is surrounded by six ligands at the corners of an octahedron. This arrangement is typical for transition metals.

2. **Identify the Central Metal Atom**:
- Look at the transition metals in the periodic table, particularly those in groups 3 to 12. These metals often have the ability to form octahedral complexes.

3. **Consider the Ligands**:
- Ligands can be classified as strong field or weak field based on their ability to split the d-orbitals of the central metal atom. Strong field ligands tend to lead to low-spin complexes, while weak field ligands lead to high-spin complexes.

4. **Determine Electron Configuration**:
- For the central metal atom, determine its electron configuration and identify the d-orbital occupancy. This will help predict whether it can accommodate six ligands in an octahedral arrangement.

5. **Check for Coordination Number**:
- An outer octahedral complex will have a coordination number of 6. Ensure that the metal can coordinate with six ligands.

6. **Evaluate the Stability**:
- Some metal-ligand combinations are more stable than others. Evaluate which combinations lead to stable octahedral complexes.

7. **Conclusion**:
- Based on the above steps, identify the specific shells or metal-ligand combinations that can form outer octahedral complexes.