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 solve the question regarding the correct statements for both fluorite and antifluorite structures, we will analyze each statement step by step.

### Step 1: Analyze Statement (i)
**Statement:** Coordination number of cation is 8.

- **Fluorite Structure (CaF2):** In this structure, the cation (Ca²⁺) has a coordination number of 8, as it is surrounded by 8 fluoride ions (F⁻).
- **Antifluorite Structure (Na2O):** In this structure, the cation (Na⁺) has a coordination number of 4, as it occupies tetrahedral voids formed by the oxide ions (O²⁻).

**Conclusion:** This statement is incorrect for antifluorite structure.

### Step 2: Analyze Statement (ii)
**Statement:** Number of formula units in one unit cell is 4.

- **Fluorite Structure:** The formula unit is CaF2. There are 4 Ca²⁺ ions and 8 F⁻ ions in the unit cell, leading to an effective number of formula units (Z) of 4.
- **Antifluorite Structure:** The formula unit is Na2O. There are also 4 Na⁺ ions and 4 O²⁻ ions in the unit cell, leading to an effective number of formula units (Z) of 4.

**Conclusion:** This statement is correct for both structures.

### Step 3: Analyze Statement (iii)
**Statement:** 100% tetrahedral voids are occupied.

- **Fluorite Structure:** In CaF2, the fluoride ions occupy all the tetrahedral voids.
- **Antifluorite Structure:** In Na2O, the sodium ions occupy all the tetrahedral voids.

**Conclusion:** This statement is correct for both structures.

### Step 4: Analyze Statement (iv)
**Statement:** Radius ratio of cation and anion is 0.20.

- **Fluorite Structure:** The radius ratio of Ca²⁺ to F⁻ is not equal to 0.20.
- **Antifluorite Structure:** The radius ratio of Na⁺ to O²⁻ is also not equal to 0.20.

**Conclusion:** This statement is incorrect for both structures.

### Final Conclusion:
The correct statements for both fluorite and antifluorite structures are:
- Statement (ii): Number of formula units in one unit cell is 4.
- Statement (iii): 100% tetrahedral voids are occupied.

Thus, the correct answer is that statements (ii) and (iii) are correct.