Final answer:
Hydrogen bonds occur when a hydrogen atom bonded to a highly electronegative atom like fluorine, oxygen, or nitrogen is also attracted to an electronegative atom in a neighboring molecule.
Step-by-step explanation:
A hydrogen bond is defined as an attractive interaction where a hydrogen atom is covalently bound to a highly electronegative atom, such as oxygen, nitrogen, or fluorine, in one molecule, and is simultaneously attracted to a lone pair of electrons on a highly electronegative atom in a neighboring molecule. Specifically, hydrogen bonds can occur when hydrogen is bonded to one of the three most electronegative elements: fluorine (F), oxygen (O), or nitrogen (N). These bonds are a special type of dipole-dipole interaction and are significantly stronger than most other types of dipole interactions, but they are still much weaker than covalent bonds. A typical hydrogen bond is about 5% as strong as a covalent bond.