One of the most prevalent intermolecular forces in biochemistry is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. The hydrogen then has the partial positive charge. The hydrogen bond is a type of dipole.  The electronegative atom must have one or more unshared electron pairs as in the case of oxygen and nitrogen, and has a negative partial charge. The hydrogen, which has a partial positive charge tries to find another atom of oxygen or nitrogen with excess electrons to share and is attracted to the partial negative charge. This forms the basis for the hydrogen bond. Hydrogen bonding is usually stronger than normal dipole forces between molecules. Hydrogen bonding is not as strong as normal covalent bonds within a molecule.