Which of the following given statement(s) is/are correct for both fluorite and antifluorite structures? (i) coordination number of cation is 8 (ii) Number of formula unit is one unit cell is 4 (iii) 100% tetrahedral voids are occupied (iv) Radius ratio of cation and anion is 0.20

Options

A. (i) and (ii)
B. (i), (ii) & (iii)
C. (ii) and (iii)
D. (i), (ii), (iii) & (iV)

Answer

To determine which statements are correct for both fluorite and antifluorite structures, we will analyze each statement one by one based on the characteristics of these structures.

### Step-by-Step Solution:

1. **Understanding Fluorite and Antifluorite Structures**:
- Fluorite (CaF2) and antifluorite (e.g., Na2O) structures are both types of ionic crystal lattices.
- In the fluorite structure, the cations are in a face-centered cubic (FCC) arrangement, and the anions occupy the tetrahedral voids.
- In the antifluorite structure, the anions are in the FCC arrangement, and the cations occupy the tetrahedral voids.

2. **Analyzing Statement (i)**: "Coordination number of cation is 8".
- In both structures, the coordination number of the cation is indeed 8. This is because each cation is surrounded by 8 anions in the fluorite structure and by 8 anions in the antifluorite structure.
- **Conclusion**: This statement is **correct**.

3. **Analyzing Statement (ii)**: "Number of formula units in one unit cell is 4".
- For the FCC lattice, there are 4 formula units per unit cell. This holds true for both fluorite and antifluorite structures.
- **Conclusion**: This statement is **correct**.

4. **Analyzing Statement (iii)**: "100% tetrahedral voids are occupied".
- In both fluorite and antifluorite structures, 100% of the tetrahedral voids are indeed occupied by the respective cations or anions.
- **Conclusion**: This statement is **correct**.

5. **Analyzing Statement (iv)**: "Radius ratio of cation and anion is 0.20".
- The radius ratio for stable ionic compounds varies. For fluorite, the radius ratio is approximately 0.414, which does not match the given 0.20.
- **Conclusion**: This statement is **incorrect**.

### Final Conclusion:
The correct statements for both fluorite and antifluorite structures are:
- (i) Coordination number of cation is 8: **Correct**
- (ii) Number of formula units in one unit cell is 4: **Correct**
- (iii) 100% tetrahedral voids are occupied: **Correct**
- (iv) Radius ratio of cation and anion is 0.20: **Incorrect**

Thus, the correct statements are (i), (ii), and (iii).