Amongst `LiCl, RbCl, BeCl_2` and `MgCl_2,` the compounds whith the greatrest and the least ionic character respecitely are :

Options

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

Answer

To determine which of the compounds LiCl, RbCl, BeCl₂, and MgCl₂ has the greatest and least ionic character, we can analyze the ionic character based on the size of the cations and their positions in the periodic table.

### Step-by-Step Solution:

1. **Understanding Ionic Character**: Ionic character refers to the degree to which a compound exhibits ionic bonding. It is influenced by the size and charge of the cations and anions involved. Generally, larger cations tend to have higher ionic character because they can more easily lose their electrons.

2. **Identify the Cations**: The cations in the given compounds are:
- Li⁺ from LiCl
- Rb⁺ from RbCl
- Be²⁺ from BeCl₂
- Mg²⁺ from MgCl₂

3. **Compare Cation Sizes**:
- Li⁺ (Lithium) is smaller than Rb⁺ (Rubidium).
- Be²⁺ (Beryllium) is smaller than Mg²⁺ (Magnesium).
- Among the cations, Rb⁺ is the largest, and Be²⁺ is the smallest.

4. **Determine Ionic Character Trends**:
- As we move down a group in the periodic table, the ionic character increases due to the increase in size of the cations. Therefore, RbCl, which contains Rb⁺, will have the greatest ionic character.
- Conversely, as we move across a period, the ionic character decreases with decreasing size. Be²⁺ is smaller than Li⁺ and Mg²⁺, leading to a lower ionic character for BeCl₂.

5. **Conclusion**:
- The compound with the **greatest ionic character** is **RbCl** (due to the large size of Rb⁺).
- The compound with the **least ionic character** is **BeCl₂** (due to the small size of Be²⁺).

### Final Answer:
- The compounds with the greatest and least ionic character respectively are **RbCl** and **BeCl₂**.