Most compounds contain polar covalent bonds. This type of
bonding is actually somewhere between the nonpolar covalent bonds
and ionic bonding.
The difference in electronegativities of atoms
joined by a chemical bond allows us to classify the type of bond.
In general, let x be the difference in
electronegativity between bonding atoms.
if  | then the bond is nonpolar covalent |
if  | then the bond is polar covalent |
if  | then the bond is ionic |
For example,
| Compound | x | Bond type |
| H2 | 2.1 - 2.1 = 0 | nonpolar covalent |
| HCl | 3.0 - 2.1 =0.9 | polar covalent |
| NaCl | 3.0 - 0.9 = 2.1 | ionic |
