List the following in order of increasing difference in electronegativity: ionic bond, pure covalent bond, polar covalent bond.

Explanation:

For example, in NaCl there is large electronegativity difference between Na and Cl. As a result, chlorine being more electronegative will attract valence electron of Na.

Hence, there will be development of partial positive charge on Na and partial negative charge will develop on Cl.

An ionic bond will always form between a metal and a non-metal.

For example, in HCl there will be a formation of a polar covalent bond as sharing of electron is taking place between H and Cl.

And, due to electronegativity difference there will be partial positive charge on H and partial negative charge on chlorine.

For example, is a pure covalent compound as there is zero electronegativity difference between both Cl atoms.

Thus, we can conclude that order of increasing difference in electronegativity will be as follows.

                pure covalent bond < polar covalent bond < ionic bond