In a complex, the highest possible coordination number is

Options

A. 6
B. 12
C. 4
D. 8

Answer

To determine the highest possible coordination number in a complex, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Coordination Number**: The coordination number of a complex refers to the number of ligand atoms that are bonded to the central metal atom or ion.

2. **Common Coordination Numbers**: Coordination numbers can typically be 2, 4, or 6. For example:
- **Coordination Number 2**: Linear complexes (e.g., Ag(NH3)2+)
- **Coordination Number 4**: Tetrahedral (e.g., [CuCl4]2-) or square planar (e.g., [Ni(CN)4]2-)
- **Coordination Number 6**: Octahedral complexes (e.g., [Co(NH3)6]3+)

3. **Exploring Higher Coordination Numbers**: While 2, 4, and 6 are common, we can also consider higher coordination numbers:
- Coordination number 8 is possible, typically in complexes with larger metal ions and specific ligands (e.g., [Mo(CN)8]4-).
- Coordination number 12 is rare and typically not observed in stable complexes.

4. **Conclusion on Maximum Coordination Number**: Based on the above information, the highest coordination number that can be reasonably expected in coordination chemistry is 8.

5. **Final Answer**: Therefore, the highest possible coordination number in a complex is **8**.