Select the incorrect statement in a CsCl crystal:

Options

A. (a) `Cs^(+)` forms a simple cubic lattice, `Cl^(-)` forms a simple cubic lattice
B. (b) `Cl^(-)` occupies body centre of `Cs^(+)`
C. (c) `Cs^(+)` occupies body centre of `Cl^(-)`
D. (d) It is impossible for `Cl^(-)` to occupy body centre of
`Cs^(+)`
because the body centre void of `Cs^(+)` is smaller than `Cl^(-)`

Answer

To solve the question regarding the incorrect statement in a CsCl crystal, let's analyze the structure and the statements provided step by step.

### Step-by-Step Solution:

1. **Understanding the CsCl Structure**:
- CsCl (Cesium Chloride) forms a simple cubic lattice structure. In this structure, Cs⁺ ions and Cl⁻ ions are arranged in a specific manner.

2. **Identifying the Positions of Ions**:
- In the CsCl crystal, the Cs⁺ ions are located at the corners of the cube, and the Cl⁻ ions occupy the body center of the cube. This means that for every unit cell of CsCl, there are Cs⁺ ions at the eight corners and one Cl⁻ ion at the center.

3. **Evaluating the Statements**:
- **Statement A**: "Cs⁺ forms a simple cubic lattice."
- This statement is true because Cs⁺ ions occupy the corners of the cubic lattice.
- **Statement B**: "Cl⁻ occupies the body center of Cs⁺."
- This statement is also true as Cl⁻ ions are indeed located at the body center of the unit cell.
- **Statement C**: "Cs⁺ occupies the body center of Cl⁻."
- This statement is true as well, since in the arrangement, Cs⁺ ions can be considered to occupy the body center position relative to the Cl⁻ ions.
- **Statement D**: "It is impossible for Cl⁻ to occupy the body center of Cs⁺."
- This statement is incorrect. As established, Cl⁻ does occupy the body center of the Cs⁺ ions in the CsCl structure.

4. **Conclusion**:
- The incorrect statement among the options provided is **Statement D**: "It is impossible for Cl⁻ to occupy the body center of Cs⁺."

### Final Answer:
The incorrect statement in a CsCl crystal is: **"It is impossible for Cl⁻ to occupy the body center of Cs⁺."**

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