CsCl has coordination number ratio

Options

A. `6:6`
B. `8:8`
C. `4:4`
D. None of these

Answer

To determine the coordination number ratio for CsCl, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of CsCl**:
- CsCl consists of cesium (Cs) and chlorine (Cl) ions. In this compound, cesium is electropositive and chlorine is electronegative.

2. **Determine the Positions of Ions**:
- In the CsCl crystal structure, cesium ions occupy the body center of the cubic lattice, while chlorine ions are located at the corners of the cube.

3. **Visualize the Unit Cell**:
- Draw a cube to represent the unit cell. Mark the cesium ion at the body center and the chlorine ions at each of the 8 corners of the cube.

4. **Calculate the Number of Atoms in the Unit Cell**:
- For the chlorine ions at the corners: Each corner atom contributes \( \frac{1}{8} \) of an atom to the unit cell, and since there are 8 corners, the total contribution from chlorine is:
\[ \text{Contribution from Cl} = 8 \times \frac{1}{8} = 1 \text{ Cl atom} \]
- For the cesium ion at the body center: It contributes fully as it is entirely within the unit cell:
\[ \text{Contribution from Cs} = 1 \text{ Cs atom} \]

5. **Determine the Coordination Number**:
- The coordination number is defined as the number of nearest neighboring atoms surrounding a central atom.
- For the cesium ion at the body center, it is surrounded by 8 chlorine ions located at the corners. Thus, the coordination number of Cs is 8.
- For the chlorine ions at the corners, each corner ion is also surrounded by 8 cesium ions from adjacent unit cells, giving it a coordination number of 8 as well.

6. **Establish the Coordination Number Ratio**:
- Since both the cesium and chlorine ions have a coordination number of 8, the coordination number ratio can be expressed as:
\[ \text{Coordination Number Ratio} = 8 : 8 \]

### Final Answer:
The coordination number ratio for CsCl is **8:8**.

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