Which are ionic compounds?

Options

A. `ZnCl_(2)`
B. `LiCl`
C. `HgCl_(2)`
D. `AgCl`

Answer

To determine which compounds are ionic, we can apply Fajans' rule, which helps us understand the nature of bonding based on the size and charge of cations and anions. Here’s a step-by-step solution to the question:

### Step-by-Step Solution:

1. **Understanding Fajans' Rule**:
- Fajans' rule states that the nature of bonding (ionic or covalent) in a compound can be predicted based on the polarizing power of cations and the polarizability of anions.
- Smaller cations with high charge have more polarizing power, while larger anions are more polarizable.

2. **Identifying Ionic Compounds**:
- Ionic compounds typically consist of larger cations with low charge and smaller anions. This combination leads to a strong electrostatic attraction, resulting in ionic bonding.

3. **Analyzing Each Compound**:
- **Syndichloride (SnCl2)**:
- The cation (Sn) is relatively large, and the anion (Cl) is small. This fits the criteria for ionic compounds. **Conclusion: Ionic.**

- **Elixyl (LiCl)**:
- Although Li is a small cation, it is paired with a larger anion (Cl). Despite the small size of the cation, it is still considered ionic due to its alkali metal nature. **Conclusion: Ionic, but less ionic than others.**

- **Mercury(II) Chloride (HgCl2)**:
- Here, Hg is a small cation with a high charge, and Cl is a relatively larger anion. According to Fajans' rule, this combination leads to covalent character. **Conclusion: Covalent.**

- **Mercury(I) Chloride (HgCl)**:
- Hg has a lower charge and is paired with a small anion (Cl). This fits the criteria for ionic compounds. **Conclusion: Ionic.**

4. **Final Summary**:
- From the analysis:
- **Ionic Compounds**: Syndichloride (SnCl2), Elixyl (LiCl), Mercury(I) Chloride (HgCl).
- **Covalent Compound**: Mercury(II) Chloride (HgCl2).