In which of the following, cation occupies cubic void.

Options

A. `AgCl`
B. `NH_(4)Cl`
C. `LiCl`
D. `HgS`

Answer

To solve the question "In which of the following, cation occupies cubic void?", we will analyze each of the given compounds one by one to determine where the cation is located in the crystal structure.

### Step-by-Step Solution:

1. **Understanding the Options**: The options provided are:
- (a) AgCl (Silver Chloride)
- (b) NH4Cl (Ammonium Chloride)
- (c) LiCl (Lithium Chloride)
- (d) HGS (Mercury Sulfide)

2. **Analyzing AgCl**:
- AgCl has a NaCl-type structure.
- In this structure, the chloride ions (Cl⁻) occupy the face-centered cubic (FCC) lattice points, while the silver ions (Ag⁺) occupy the octahedral voids.
- **Conclusion**: The cation does not occupy a cubic void.

3. **Analyzing NH4Cl**:
- NH4Cl adopts a cesium chloride-like structure.
- In this structure, the chloride ions (Cl⁻) are located at the corners of the cube, and the ammonium ions (NH4⁺) occupy the body-centered cubic (BCC) position.
- **Conclusion**: The cation (NH4⁺) occupies a cubic void (specifically, the body center).

4. **Analyzing LiCl**:
- Similar to AgCl, LiCl also has a NaCl-type structure.
- The chloride ions occupy the FCC lattice points, and the lithium ions occupy the octahedral voids.
- **Conclusion**: The cation does not occupy a cubic void.

5. **Analyzing HGS**:
- HGS (Mercury Sulfide) has a structure similar to that of zinc sulfide (ZnS), which is a sphalerite structure.
- In this structure, the sulfide ions (S²⁻) occupy the FCC lattice points, while the mercury ions (Hg²⁺) occupy the tetrahedral voids.
- **Conclusion**: The cation does not occupy a cubic void.

6. **Final Conclusion**:
- After analyzing all the options, we find that the only compound where the cation occupies a cubic void is **NH4Cl**.

### Answer:
The correct answer is **NH4Cl**.