Final answer:
When there are polar molecules and H atoms are bonded to N, O, or F atoms, strong intermolecular forces like hydrogen bonding occur. These forces are a result of the large difference in electronegativity between hydrogen and the electronegative atoms. The small size of a hydrogen atom allows these dipoles to approach one another closely, leading to the formation of very strong dipole-dipole interactions called hydrogen bonds.
Step-by-step explanation:
Strong intermolecular forces, such as hydrogen bonding, occur when there are polar molecules and H atoms are bonded to N, O, or F atoms. In these cases, the large difference in electronegativity between hydrogen and the electronegative atoms (O, N, or F) results in a large partial positive charge on hydrogen and a correspondingly large partial negative charge on the electronegative atom.
This leads to the formation of strong bond dipoles that can interact strongly with each other. Because of the small size of a hydrogen atom, these dipoles can approach one another more closely than other dipoles, resulting in very strong dipole-dipole interactions called hydrogen bonds.