The coordination number `Cs` and `Br` in `CsBr` are, respectively,

Options

A. `8,8`
B. `6,6`
C. `8,6`
D. `6,8`

Explanation

To determine the coordination numbers of Cs and Br in CsBr, we can follow these steps:

### Step 1: Understand the Structure of CsBr
In the crystal structure of CsBr, the cesium ions (Cs⁺) and bromide ions (Br⁻) are arranged in a specific manner. Cs⁺ ions are located at the body center of the cubic unit cell, while Br⁻ ions are located at the corners of the cube.

### Step 2: Identify the Coordination Number of Cs⁺
The coordination number is defined as the number of nearest neighbors surrounding a particular ion. In the case of Cs⁺, which is located at the body center of the cube, it is surrounded by the Br⁻ ions located at the corners of the cube.

- There are 8 corners in a cube, and each corner Br⁻ ion is a nearest neighbor to the Cs⁺ ion.
- Therefore, the coordination number of Cs⁺ is 8.

### Step 3: Identify the Coordination Number of Br⁻
Now, we will determine the coordination number for Br⁻ ions. Since Br⁻ ions are located at the corners of the cube, we need to consider how many Cs⁺ ions are nearest to each Br⁻ ion.

- Each Br⁻ ion at the corner of the cube is also surrounded by Cs⁺ ions.
- Since there is one Cs⁺ ion at the body center that is in contact with all 8 corner Br⁻ ions, each Br⁻ ion has 8 nearest neighbors (the Cs⁺ ions).
- Therefore, the coordination number of Br⁻ is also 8.

### Step 4: Conclusion
From the above analysis, we conclude that:
- The coordination number of Cs⁺ in CsBr is 8.
- The coordination number of Br⁻ in CsBr is also 8.

Thus, the final answer is:
**The coordination numbers of Cs and Br in CsBr are 8 and 8, respectively.**