How many `Cs^+` ions occupy the second nearest neighbour location of a `Cs^+` ion in the structure CsCl (8:8 coordination ) ?

Options

A. 8
B. 6
C. 16
D. 10

Answer

To solve the question of how many `Cs^+` ions occupy the second nearest neighbor location of a `Cs^+` ion in the structure of CsCl (8:8 coordination), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of CsCl**:
- CsCl crystallizes in a body-centered cubic (BCC) structure. In this structure, the `Cs^+` ions are located at the center of the unit cell, while the `Cl^-` ions occupy the corners of the cube.

2. **Identify the Coordination Number**:
- In the CsCl structure, each `Cs^+` ion has a coordination number of 8, meaning it is surrounded by 8 `Cl^-` ions.

3. **Determine the Nearest Neighbors**:
- The first nearest neighbors of a `Cs^+` ion are the `Cl^-` ions located at the corners of the cube. There are 8 `Cl^-` ions surrounding one `Cs^+` ion.

4. **Identify the Second Nearest Neighbors**:
- The second nearest neighbors of a `Cs^+` ion are the `Cs^+` ions located in adjacent unit cells. Specifically, in a BCC structure, the second nearest neighbors are the `Cs^+` ions located at the center of the adjacent unit cells.

5. **Count the Second Nearest Neighbors**:
- For a given `Cs^+` ion at the center of a unit cell, there are 6 adjacent unit cells (one above, one below, and one on each of the 4 sides) that each contain a `Cs^+` ion at their centers. Therefore, there are 6 `Cs^+` ions that are the second nearest neighbors.

6. **Conclusion**:
- Thus, the total number of `Cs^+` ions occupying the second nearest neighbor location of a `Cs^+` ion in the CsCl structure is **6**.

### Final Answer:
The answer is **6**.

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