Which of the following is hcp crystal structure ?

Options

A. NaCl
B. CsCl
C. Zn
D. RbCl

Explanation

To determine which of the following options exhibits a hexagonal close-packed (HCP) crystal structure, we can analyze each option systematically:

### Step 1: Understand HCP Structure
HCP, or hexagonal close packing, is a type of crystal structure characterized by a hexagonal arrangement of atoms. In HCP, each atom is surrounded by 12 others, and the arrangement consists of two layers of atoms stacked in a specific way.

### Step 2: Analyze the Given Options
1. **NaCl (Sodium Chloride)**:
- NaCl has a face-centered cubic (FCC) structure. In this structure, the sodium ions (Na⁺) occupy the face centers and corners of the cube, while the chloride ions (Cl⁻) fill the octahedral voids.
- **Conclusion**: NaCl is not HCP.

2. **CsCl (Cesium Chloride)**:
- CsCl exhibits a body-centered cubic (BCC) structure. In this arrangement, cesium ions (Cs⁺) occupy the body center of the cube, and chloride ions (Cl⁻) occupy the corners.
- **Conclusion**: CsCl is not HCP.

3. **RbCl (Rubidium Chloride)**:
- RbCl can exhibit a structure that lies between FCC and BCC depending on the conditions. However, it does not specifically represent the HCP structure.
- **Conclusion**: RbCl is not HCP.

4. **Option C (Assuming it's a known HCP compound)**:
- If option C is a known compound that exhibits HCP, such as magnesium (Mg) or zinc (Zn), then it would be the correct answer.
- **Conclusion**: If option C is indeed a known HCP compound, then it is the correct answer.

### Step 3: Final Conclusion
After analyzing all the options, the only compound that exhibits a hexagonal close-packed structure is option C (assuming it is a known HCP compound).

### Answer:
**Option C is the correct answer as it exhibits the HCP crystal structure.**

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