Assertion (A) : In sodium chloride crystal, `Na^(o+)` ions occupy `OVs` while `Cl^(ɵ)` ions occupy vertices of octahedron.
Reason (R ) : The radius ratio of `Na^(o+) : Cl^(ɵ)` lies between `0.4` and `0.7`.

Options

A. If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`
B. If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`
C. If `(A)` is correct, but `(R)` is incorrect.
D. If both `(A)` is incorrect, but `(R)` is correct.

Explanation

To solve the given question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that in sodium chloride (NaCl) crystal, Na⁺ ions occupy octahedral voids while Cl⁻ ions occupy the vertices of the octahedron.
- In a NaCl crystal structure, Na⁺ ions are indeed found in the octahedral voids, and Cl⁻ ions are located at the corners and face centers of the cubic unit cell.
- Therefore, **Assertion (A) is correct**.

2. **Understanding the Reason (R)**:
- The reason states that the radius ratio of Na⁺ to Cl⁻ lies between 0.4 and 0.7.
- The radius ratio (r) is calculated as \( r = \frac{R_{Na^+}}{R_{Cl^-}} \).
- For NaCl, the radius of Na⁺ is approximately 0.102 nm and the radius of Cl⁻ is approximately 0.181 nm.
- Thus, the radius ratio \( r \approx \frac{0.102}{0.181} \approx 0.564 \), which indeed lies between 0.4 and 0.7.
- Therefore, **Reason (R) is also correct**.

3. **Analyzing the Relationship Between A and R**:
- While both A and R are correct, we need to determine if R is the correct explanation of A.
- The assertion about the positions of Na⁺ and Cl⁻ ions in the crystal lattice does not depend solely on the radius ratio. The arrangement is based on the ionic sizes and the coordination number, which is a separate concept.
- Thus, **R is not the correct explanation of A**.

4. **Conclusion**:
- Since both A and R are correct, but R does not explain A, the correct answer is:
- **Option B: Both A and R are correct, but R is not the correct explanation of A**.