Assertion (A) : `CsCl` crystal, the coordination number of `Cs^(o+)` ion is `8`.
Reason (R ) : `Cl^(ɵ)` ion in `CsCl` adopt bcc type of packing,

Options

A. If both assertion and reason are correct and reason is correct explanation for assertion
B. If both assertion and reason are correct but reason is not correct explanation for assertion
C. If assertion is correct but reason is incorrect
D. If both assertion and reason are incorrect

Explanation

To analyze the given assertion and reason regarding the CsCl crystal structure, we can break down the solution into several steps:

### Step-by-Step Solution

1. **Understanding the Assertion**:
- The assertion states that in a CsCl crystal, the coordination number of the Cs⁺ ion is 8.
- Coordination number refers to the number of nearest neighbor ions surrounding a central ion.

2. **Analyzing the CsCl Structure**:
- CsCl crystallizes in a body-centered cubic (BCC) lattice structure.
- In this structure, the Cs⁺ ions occupy the body center of the cube, while the Cl⁻ ions are located at the corners of the cube.

3. **Determining the Coordination Number**:
- In a BCC lattice, the body-centered atom (Cs⁺) is surrounded by 8 corner atoms (Cl⁻).
- Therefore, the coordination number of the Cs⁺ ion is indeed 8, as it is in contact with the 8 Cl⁻ ions located at the corners.

4. **Understanding the Reason**:
- The reason states that the Cl⁻ ion in CsCl adopts BCC type of packing.
- However, this statement is incorrect because the Cl⁻ ions only occupy the corners of the cube, which corresponds to a simple cubic (SCC) packing, not BCC.

5. **Conclusion**:
- The assertion is true because the coordination number of Cs⁺ is 8.
- The reason is false because Cl⁻ does not adopt BCC packing; it adopts SCC packing.
- Therefore, the correct conclusion is that the assertion is correct, but the reason is incorrect.

### Final Answer
- The assertion is true, and the reason is false.