The number of equidistant oppositely charged ions in a sodium chloride crystal is:

Options

A. 8
B. 6
C. 4
D. 2

Answer

To solve the question regarding the number of equidistant oppositely charged ions in a sodium chloride (NaCl) crystal, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of NaCl**:
Sodium chloride (NaCl) crystallizes in a face-centered cubic (FCC) lattice structure. In this structure, the chloride ions (Cl⁻) form the FCC lattice, while the sodium ions (Na⁺) occupy the octahedral voids.

2. **Identifying the Positions of Ions**:
In the FCC structure, each unit cell contains 4 Cl⁻ ions. The Na⁺ ions are located in the octahedral voids, which are present at the center of the unit cell and at the edge centers.

3. **Determining the Number of Equidistant Oppositely Charged Ions**:
Each Na⁺ ion in the octahedral void is surrounded by Cl⁻ ions. To find the number of Cl⁻ ions that are equidistant from a single Na⁺ ion, we can visualize the arrangement:
- The Na⁺ ion at the center of the octahedral void has Cl⁻ ions located at the corners of the octahedron.

4. **Counting the Cl⁻ Ions**:
For each Na⁺ ion, there are 6 Cl⁻ ions surrounding it at equal distances (one on each face of the octahedron). Therefore, the number of equidistant oppositely charged ions (Cl⁻ ions) around a single Na⁺ ion is 6.

5. **Conclusion**:
Thus, the number of equidistant oppositely charged ions in a sodium chloride crystal is **6**.

### Final Answer:
The number of equidistant oppositely charged ions in a sodium chloride crystal is **6**.