posted by Shaniquaa .
Why does MgO have a higher melting point than CaS? They are both ionic compounds with the same charges, but CaS is heavier so shouldn't it have a higher melting point?
The charge of a large ion is less concentrated because of its larger radius and surface area. That makes the attraction between Ca^2+ and S^2- ions weaker than the attraction between the smaller Mg^2+ and O^2- ions.