The regular three dimensional arrangement of points in a crystal is known as crystal lattice and the smallest repeating pattern in the lattice is called unit cell. The unit cells are characterised by the edge lengths a, b, c and the angles between them `alpha, beta and gamma` respectively. Based on this, there are seven crystal systems. In a cubic unit cell:
`a=b=c and alpha = beta=gamma=90^(@)` The number of points in simple, body centred and face centred cubic cells are 1,2 and 4 respectively In both the hcp and ccp of spheres, the number of tetrahedral voids per sphere is two while the octahedral voids is one.
The C.N of cation occuppying an octahedral vois is:

Options

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

Explanation

To determine the coordination number (C.N) of a cation occupying an octahedral void, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Octahedral Voids**:
- An octahedral void is a type of interstitial site in a crystal lattice where a smaller ion (cation) can fit between larger ions (anions).

2. **Arrangement of Atoms**:
- In an octahedral void, the cation is surrounded by six anions. This arrangement forms an octahedron shape, where the cation is at the center and the six anions are at the vertices of the octahedron.

3. **Counting Nearest Neighbors**:
- The coordination number is defined as the number of nearest neighbor atoms surrounding a central atom. In the case of an octahedral void, the cation has six neighboring anions.

4. **Conclusion**:
- Therefore, the coordination number (C.N) of a cation occupying an octahedral void is 6.

### Final Answer:
The coordination number of a cation occupying an octahedral void is **6**.

---