A hydrogen bond is a low kind type of dipole-dipole bond that exists between an electronegative molecule and a hydrogen molecule bonded to another electronegative molecule. This type of bond always involves a hydrogen molecule. That explains the name.
Hydrogen bonds can occur between molecules (intermolecularly), or within different parts of a single molecule (intramolecularly). The typical hydrogen bond is stronger than van der Waals forces, but weaker than covalent, ionic and metallic bonds.
Intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C).
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