Which compound is highest covalent:

Options

A. LiCl
B. LiF
C. LiBr
D. Lil

Explanation

To determine which compound has the highest covalent character, we can follow these steps based on the principles outlined in the video transcript.

### Step-by-Step Solution:

1. **Understand the Concept of Covalent Character**:
- According to Fajan's rules, covalent character in a compound increases when the cation is small and has a high charge, and when the anion is large.

2. **Identify the Cations and Anions**:
- For the given compounds, identify the cations (e.g., Li⁺, Na⁺, K⁺) and anions (e.g., F⁻, Cl⁻, Br⁻, I⁻).

3. **Analyze the Size of Cations**:
- The smaller the cation, the greater its polarizing power. Among the alkali metals, lithium (Li⁺) is the smallest cation.

4. **Analyze the Size of Anions**:
- The larger the anion, the more easily it can be polarized. Among the halides, iodide (I⁻) is the largest anion.

5. **Combine the Findings**:
- Since Li⁺ is a small cation and I⁻ is a large anion, the compound LiI would exhibit a significant covalent character due to the small size of Li⁺ and the large size of I⁻.

6. **Consider the Charge of Cations**:
- The charge on the cation also contributes to covalent character. A higher charge on the cation increases its polarizing ability. However, in this case, we are comparing alkali metal compounds, where the charge is typically +1.

7. **Conclusion**:
- Based on the above analysis, LiI (lithium iodide) will have the highest covalent character among the given options due to the combination of a small cation and a large anion.

### Final Answer:
The compound with the highest covalent character is **LiI (Lithium Iodide)**.

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