Firstly, An ionic bond results when the sharing is so unequal that fully charged ions form. Electronegativity difference can be used to predict bond type. Secondly, one method to classify bonds based on this difference can be described as follows. If the electronegativities differ by less than 0.4 units, the bond can be classified as nonpolar covalent. If the difference is between 0.4 and 2.0 units, the bond is classified as polar covalent, and if the difference is more than 2.0 units, the bond is substantially ionic.
