Choose the compounds of maximum and minimum ionic character from LiCl, RbCl, `BeCl_(2) and MgCl_(2)`

Options

A. LiCl and RbCl
B. RbCl and `BeCl_(2)`
C. RbCl and `MgCl_(2)`
D. `MgCl_(2) and BeCl_(2)`

Answer

To determine the compounds with maximum and minimum ionic character from the given options (LiCl, RbCl, BeCl₂, and MgCl₂), we can utilize Fajans' rules. Here’s a step-by-step solution:

### Step 1: Understand Fajans' Rules
Fajans' rules state that the covalent character of an ionic compound increases with:
- The charge on the cation (positive ion).
- The smaller size of the cation.

Conversely, the ionic character decreases as covalent character increases. Therefore, the compound with the highest covalent character will have the lowest ionic character, and vice versa.

### Step 2: Identify the Cations and Their Charges
The cations in the compounds are:
- Li⁺ (Charge +1)
- Rb⁺ (Charge +1)
- Be²⁺ (Charge +2)
- Mg²⁺ (Charge +2)

### Step 3: Compare the Sizes of the Cations
- Li⁺ is smaller than Rb⁺.
- Be²⁺ is smaller than Mg²⁺.

### Step 4: Determine Covalent Character
Among the cations:
- Be²⁺ has the highest charge (+2) and is smaller than Mg²⁺, leading to a higher covalent character for BeCl₂.
- Li⁺ has a smaller size compared to Rb⁺, but both have a +1 charge.

### Step 5: Identify Maximum and Minimum Ionic Character
- **Minimum Ionic Character**: Since BeCl₂ has the highest covalent character due to the small size and high charge of Be²⁺, it will have the minimum ionic character.
- **Maximum Ionic Character**: RbCl will have the maximum ionic character because Rb⁺ is larger and has a +1 charge, leading to lower covalent character compared to LiCl.

### Conclusion
- **Maximum Ionic Character**: RbCl
- **Minimum Ionic Character**: BeCl₂

Thus, the compounds with maximum and minimum ionic character are RbCl and BeCl₂, respectively.

### Final Answer
- Maximum Ionic Character: **RbCl**
- Minimum Ionic Character: **BeCl₂**

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