which compound should require the highest tem...

# Answer: D. Na₂O # Explanation: ## Step1: Consider lattice energy Lattice energy affects melting point. Higher lattice energy means higher melting point. ## Step2: Analyze ionic charge and radius - For ionic compounds, lattice energy is related to ionic charge and ionic radius. - In Na₂O, \(O^{2 -}\) has a higher charge (\(z = 2\)) compared to \(F^{-}(z = 1)\) in NaF and LiF. In LiCl, \(Cl^{-}\) has a larger radius than \(O^{2 -}\) (and lower charge). - According to Coulomb's law \(U=\frac{kq_1q_2}{r}\) (where \(U\) is lattice energy, \(k\) is a constant, \(q_1\) and \(q_2\) are ionic charges, \(r\) is the distance between ions). - For Na₂O, with higher ionic charge (\(q_1 = 1\) for \(Na^{+}\), \(q_2=2\) for \(O^{2 -}\)) and relatively small ionic radii (compared to some other combinations), it has a higher lattice energy. So Na₂O should require the highest temperature to melt.