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In addition to the three strong primary bonds discussed above, there are also several much weaker (and therefore called secondary) bonds which provide the interatomic attractive forces that hold some types of atoms together in a solid material. These forces are referred to as either secondary bonds, molecular bonds, or van der Waals bonds. These bonds are due to residual electrostatic fields between neutral molecules whose charge distribution is not uniform.

Covalently bonded atoms frequently form molecules that behave as electric or magnetic dipoles. Although the molecule itself is electrically neutral, there is an elec­trical imbalance within the molecule. That is, the center of the positive charge and the center of the negative charge do not coincide, and it is this dipole that creates molecular bonding.