In the crystals of which of the following ionic compounds would you expect maximum distance between the centres of the cations and anion?

Options

A. `LiF`
B. `CsF`
C. `Csl`
D. `LiI`

Explanation

To determine which ionic compound has the maximum distance between the centers of the cations and anions, we need to analyze the sizes of the cations and anions in each compound. The larger the cation and anion, the greater the distance between their centers.

**Step-by-Step Solution:**

1. **Identify the Ionic Compounds:**
The given ionic compounds are:
- LiF (Lithium Fluoride)
- CsF (Cesium Fluoride)
- CsI (Cesium Iodide)
- LiI (Lithium Iodide)

2. **Determine the Sizes of Cations and Anions:**
- **Li⁺ (Lithium Ion)**: Small cation
- **F⁻ (Fluoride Ion)**: Small anion
- **Cs⁺ (Cesium Ion)**: Large cation
- **I⁻ (Iodide Ion)**: Large anion

3. **Analyze Each Compound:**
- **LiF**: Li⁺ is small and F⁻ is small, resulting in a small distance between them.
- **CsF**: Cs⁺ is large, but F⁻ is small, resulting in a moderate distance.
- **CsI**: Cs⁺ is large and I⁻ is large, resulting in a large distance between them.
- **LiI**: Li⁺ is small and I⁻ is large, resulting in a moderate distance.

4. **Compare the Distances:**
- The distance between the centers of Li⁺ and F⁻ is small.
- The distance between the centers of Cs⁺ and F⁻ is moderate.
- The distance between the centers of Cs⁺ and I⁻ is the largest.
- The distance between the centers of Li⁺ and I⁻ is moderate.

5. **Conclusion:**
The compound with the maximum distance between the centers of the cation and anion is **CsI (Cesium Iodide)**, as it contains the largest cation (Cs⁺) and the largest anion (I⁻).

**Final Answer: CsI (Cesium Iodide)**

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