Molecules are held together by ________.

The Ionic bond has the difference in the electronegativity of the constituent atoms like that two separate ions (cation and anion) are formed and the Covalent bond, rather than the transfer of electrons, requires the sharing of the valence electrons between the two atoms. 

• The bond present in the molecules could be ionic or covalent depending on the difference in the electronegativity of the atoms.