Which of the following substances has the highest melting point? — Chemical Bonding Chemistry Question

💡 Solution & Explanation

Step 1: The melting point of ionic solids is directly proportional to their lattice energy. Step 2: Lattice energy is proportional to the product of ionic charges (q1 * q2) and inversely proportional to the interionic distance (r_c + r_a). MgO and BaO have charges of +2 and -2 (product = 4), whereas NaCl and KCl have charges of +1 and -1 (product = 1). Step 3: Comparing MgO and CaO/SrO/BaO, since Mg^2+ is the smallest cation among the alkaline earth metals, MgO has the shortest interionic distance and therefore the highest lattice energy and melting point. Thus, option (c) is correct.