X and Y are two metals. When burnt in air, X forms only oxide while Y forms oxide and nitride. The m — s Block Elements Chemistry Question

💡 Solution & Explanation

Step 1: According to Fajans' rules, the smaller the cation, the greater its polarizing power, which increases the covalent character of the ionic bond and lowers the melting point. Step 2: Among the alkali metal chlorides, the size of the cations increases as Li+ < Na+ < K+ < Rb+ < Cs+. Step 3: Because Li+ is the smallest cation, LiCl has the highest covalent character and consequently the lowest melting point, matching option (a).