Incorrect option (s) about NaCl structure is/are

Options

A. 4 corners are shared
B. 12 edges are shared
C. 6 corners and 2 edges are shared
D. 3 edges and 3 faces are shared

Answer

To determine the incorrect options regarding the NaCl structure, we need to analyze the structure of NaCl in detail. Here’s a step-by-step solution:

### Step 1: Understanding the Structure of NaCl
NaCl (sodium chloride) crystallizes in a face-centered cubic (FCC) lattice structure. In this structure:
- Sodium ions (Na⁺) occupy the octahedral voids.
- Chloride ions (Cl⁻) are located at the corners and face centers of the FCC unit cell.

### Step 2: Counting the Ions in the Unit Cell
In a face-centered cubic unit cell:
- There are 8 corner atoms, each contributing 1/8 of an atom to the unit cell (total contribution from corners = 8 × 1/8 = 1).
- There are 6 face-centered atoms, each contributing 1/2 of an atom to the unit cell (total contribution from faces = 6 × 1/2 = 3).

Thus, the total number of Cl⁻ ions in the unit cell = 1 (from corners) + 3 (from faces) = 4 Cl⁻ ions.

### Step 3: Analyzing the Octahedral Voids
In the FCC structure, there are 4 octahedral voids per unit cell. Each Na⁺ ion occupies one of these octahedral voids.

### Step 4: Identifying Incorrect Statements
Now, we need to evaluate the options provided in the question to identify which statements are incorrect regarding the NaCl structure.

1. **Correct Statement**: Na⁺ ions occupy octahedral voids.
2. **Correct Statement**: Cl⁻ ions are located at the corners and face centers of the FCC lattice.
3. **Incorrect Statement**: The number of edges shared by the ions in the structure is not 12. Each edge of the cube is shared by 4 unit cells, and each edge contributes 1/4 of an atom to the unit cell.

### Conclusion
Based on the analysis, the incorrect option(s) about the NaCl structure would likely include any statement that misrepresents the number of edges shared or the arrangement of ions.