What is the reason magnesium oxide has a higher melting point than sodium chloride?

Magnesium oxide exhibits a higher melting point than sodium chloride primarily because magnesium oxide ions carry a greater charge than the ions in sodium chloride. In magnesium oxide, magnesium (Mg) has a +2 charge and oxygen (O) has a -2 charge, resulting in MgO being formed from ions with a total charge of +2 and -2. This leads to stronger ionic bonds due to the increased electrostatic attraction between the ions.

In contrast, sodium chloride is composed of sodium (Na) with a +1 charge and chloride (Cl) with a -1 charge, creating a system of ionic bonds that are weaker than those found in magnesium oxide. The increased charge in the magnesium oxide compound results in stronger interactions between the oppositely charged ions, which in turn necessitates a greater amount of energy to break these bonds during melting. This is why magnesium oxide has a higher melting point compared to sodium chloride.