Question

Question: Repeat the determinations of the preceding problem for the NaCl crystal, referring to Figure 21.16.

Short answer

6 Cl atoms at face centers, 12 Na at edge centers, 8 Cl atoms at corners.

Step-by-step solution

The number of nearest neighbors, and second nearest neighbors.

The structure of NaCl follows the face-centered unit cell (fcc) pattern. The sodium atoms are present at the edge center, and chlorine atoms are present at the corners and face centers.

Here, the atom on the edge center is a sodium ion, and the 6 surrounded atoms are chlorine ions.

Therefore, the first coordination number (nearest neighbors) of sodium ions is 6 chlorine ions present in different unit cells.

Later, the second nearest neighbors of sodium ions are 12 sodium ions present in the edge centers.

The third nearest neighbor of a cesium ion in crystalline CsCl.

Now, the third nearest neighbors are 8 Cl atoms at corners.