Intermolecular forces are the forces that hold molecules together in a compound. They are weaker than chemical bonds, which hold atoms together in a molecule. Hydrogen bonds are a type of intermolecular force that occurs when a hydrogen atom is bonded to a very electronegative atom, such as fluorine, oxygen, or nitrogen. The electronegative atom pulls the electrons away from the hydrogen atom, creating a partial positive charge on the hydrogen atom. This partial positive charge can then attract the partial negative charge on another electronegative atom, forming a hydrogen bond.

Hydrogen bonds are stronger than other intermolecular forces because they are electrostatic in nature. Electrostatic forces are stronger than van der Waals forces, which are the other type of intermolecular force. Van der Waals forces are caused by the temporary fluctuations in the electron clouds of molecules.

The strength of a hydrogen bond depends on the electronegativity of the atoms involved and the distance between the atoms. The more electronegative the atoms, the stronger the hydrogen bond. The shorter the distance between the atoms, the stronger the hydrogen bond.