The ionic character of a compound is inversely proportional to its covalent character. According to Fajan's rules, covalent character increases with:

• Small size of cation
• Large size of anion
• High charge on cation
• Pseudo noble gas configuration of cation (d-block elements)

In this question, all anions are Cl^-, so we need to compare the cations: Li⁺, Rb⁺, Be²⁺, Mg²⁺.

Step 1: Compare ionic character based on charge.
Compounds with +1 charge on the cation (LiCl, RbCl) will have higher ionic character than compounds with +2 charge on the cation (BeCl₂, MgCl₂). This is because a higher charge on the cation increases its polarizing power, leading to greater covalent character.

Step 2: Compare ionic character among +1 cations.
Between Li⁺ and Rb⁺, Rb⁺ is much larger than Li⁺. A larger cation has lower polarizing power, leading to higher ionic character. Therefore, RbCl has greater ionic character than LiCl.

Step 3: Compare ionic character among +2 cations.
Between Be²⁺ and Mg²⁺, Be²⁺ is much smaller than Mg²⁺. A smaller cation has higher polarizing power, leading to greater covalent character and thus lower ionic character. Therefore, BeCl₂ has the least ionic character among the given compounds.

Step 4: Conclude the greatest and least ionic character.
Based on the above analysis, RbCl has the greatest ionic character, and BeCl₂ has the least ionic character.

Option Analysis:

• A) LiCl, RbCl: LiCl does not have the greatest ionic character, and RbCl does not have the least.
• B) RbCl, MgCl₂: RbCl has the greatest ionic character, but MgCl₂ does not have the least. BeCl₂ has less ionic character than MgCl₂.
• C) RbCl, BeCl₂: RbCl has the greatest ionic character (largest cation, lowest charge), and BeCl₂ has the least ionic character (smallest cation, highest charge). This is the correct option.
• D) MgCl₂, BeCl₂: MgCl₂ does not have the greatest ionic character.

Correct Answer: (C)