In the sodium chloride structure each `Na_(o+)` ion is surrounded by six `Cl^(ɵ)` ions nearest neighbours and ……….. `Na^(o+)` ions next nearest neighbours.

Answer

To solve the question regarding the sodium chloride (NaCl) structure, we need to determine how many Na⁺ ions are the next nearest neighbors to a given Na⁺ ion, given that each Na⁺ ion is surrounded by six Cl⁻ ions as nearest neighbors.

### Step-by-Step Solution:

1. **Understanding the Structure**:
- In the NaCl structure, Na⁺ ions occupy octahedral voids, while Cl⁻ ions form a face-centered cubic (FCC) lattice.
- Each Na⁺ ion is surrounded by six Cl⁻ ions, which means the coordination number of Na⁺ is 6.

2. **Identifying Nearest Neighbors**:
- The nearest neighbors for Na⁺ are the six Cl⁻ ions. This is already given in the question.

3. **Next Nearest Neighbors**:
- The next nearest neighbors for Na⁺ ions are other Na⁺ ions.
- In the NaCl structure, the arrangement allows each Na⁺ ion to be surrounded by additional Na⁺ ions.

4. **Calculating the Distance**:
- The distance between the Na⁺ ions can be calculated based on their positions in the lattice.
- The minimum distance between two Na⁺ ions occurs when one Na⁺ is at the body center and the other is at one of the octahedral voids.

5. **Using Geometry**:
- The distance between two Na⁺ ions can be calculated using the geometry of the FCC lattice.
- The distance can be derived from the coordinates of the Na⁺ ions in the lattice.

6. **Determining Coordination Number**:
- If the distance between the Na⁺ ions is calculated as \( \frac{a}{\sqrt{2}} \) (where \( a \) is the edge length of the cube), the coordination number for these next nearest neighbors is 12.

7. **Final Answer**:
- Therefore, the number of next nearest neighbors for each Na⁺ ion in the NaCl structure is 12.

### Final Answer:
The number of Na⁺ ions as next nearest neighbors is **12**.

---