Intermolecular force refers to the attractive or repulsive forces that exist between molecules, atoms or ions. Synonyms for intermolecular force include interatomic force, van der Waals force, dipole-dipole interaction, hydrogen bond, London dispersion force, and electrostatic force. Van der Waals force is a broad term that encompasses all intermolecular forces, including London dispersion force, dipole-dipole interaction, and hydrogen bond. Electrostatic force refers specifically to the attractive force between oppositely charged ions or molecules. Dipole-dipole interactions involve the electrostatic attraction between partial positive and partial negative charges on adjacent molecules. Hydrogen bonds are a type of dipole-dipole interaction that occurs between the lone pair of electrons in a molecule and a hydrogen atom that is covalently bonded to another molecule.