When molten Zn is cooled to solid state, it assumes HCP structure. Then number of nearest neighbours of Zn atoms will be

Options

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

Answer

To determine the number of nearest neighbors of zinc atoms when it assumes a hexagonal close-packed (HCP) structure, we need to understand the coordination number of HCP.

### Step-by-Step Solution:

1. **Understanding HCP Structure**:
- The hexagonal close-packed (HCP) structure is a type of crystal lattice arrangement where atoms are closely packed together. In this arrangement, each atom is surrounded by other atoms.

2. **Coordination Number**:
- The coordination number is defined as the number of nearest neighbor atoms surrounding a central atom. For HCP, we need to visualize how many atoms are in contact with a single atom.

3. **Visualizing the Arrangement**:
- In the HCP structure, when you look at a single atom, it is surrounded by other atoms. If we visualize this:
- There are 6 atoms in the same plane (the base plane).
- Above and below this central atom, there are 3 additional atoms (one directly above and one directly below).

4. **Counting Nearest Neighbors**:
- From the base plane, the central atom touches 6 atoms surrounding it.
- Additionally, it touches 3 atoms above and 3 atoms below.
- Therefore, the total number of nearest neighbors is calculated as follows:
- Neighbors in the same plane: 6
- Neighbors above: 3
- Neighbors below: 3
- Total = 6 (side) + 3 (above) + 3 (below) = 12

5. **Conclusion**:
- Thus, the number of nearest neighbors of zinc atoms in the HCP structure is **12**.

### Final Answer:
The number of nearest neighbors of Zn atoms in HCP structure is **12**.