When molten zinc is cooled to solid state, it assumes `hcp` structure. Then the number of nearest neighbours of zinc atom will be

Options

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

Explanation

To determine the number of nearest neighbors of a zinc atom in a hexagonal close-packed (hcp) structure, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the HCP Structure**:
- In an hcp structure, each atom is surrounded by other atoms in a specific arrangement. The hcp structure consists of two layers of atoms, with one layer above the other.

2. **Visualizing the Arrangement**:
- Consider a single zinc atom at the center of the arrangement. In the hcp structure, the atom will have neighbors in both the same layer and the adjacent layers.

3. **Counting Neighbors in the Same Layer**:
- In the same layer, the zinc atom will have 6 nearest neighbors. These neighbors are positioned around it in a hexagonal arrangement.

4. **Counting Neighbors in Adjacent Layers**:
- Above and below the central atom, there are additional atoms. Each of these layers contributes 3 more nearest neighbors.
- Therefore, there are 3 atoms directly above and 3 atoms directly below the central atom.

5. **Total Nearest Neighbors Calculation**:
- Adding these together gives:
- Neighbors in the same layer: 6
- Neighbors in the layer above: 3
- Neighbors in the layer below: 3
- Total nearest neighbors = 6 (same layer) + 3 (above) + 3 (below) = 12.

6. **Conclusion**:
- Thus, the total number of nearest neighbors for a zinc atom in an hcp structure is **12**.

### Final Answer:
The number of nearest neighbors of a zinc atom in hcp structure is **12**.