An ionic bond is the electrostatic attraction between two oppositely charged ions to form an ionic compound. The greater the charge of an ion the stronger the ionic bond as the attraction between the positive nuclei and the negative outer electrons is greater and therefore the higher the melting point and boiling points are. The smaller the ionic radii of the ion the stronger the electrostatic attraction is between other ions are as they can pack closer together than larger ions . Therefore the ionic with small, closely packed ions have a higher melting point and boiling point than ionic compounds composed of large ions.