Intermolecular Interactions in the Gas Phase Gary L. Bertrand Department of Chemistry University of Missouri-Rolla Interactions between two or more molecules are called inter molecular interactions, while the interactions between the atoms within a molecule are called intra molecular interactions.
Intermolecular interactions occur between all types of molecules or ions in all states of matter.
They range from the strong, long-distance electrical attractions and repulsions between ions to the relatively weak dispersion forces which have not yet been completely explained. We will explore these various forces and interactions in the gas phase to understand why some materials vaporize at very low temperatures, and others persist as solids or liquids to extremely high temperatures. These Coulombic forces operate over relatively long distances in the gas phase. Two oppositely-charged particles flying about in a vacuum will be attracted toward each other, and the force becomes stronger and stronger as they approach until eventually they will stick together and a considerable amount of energy will be required to separate them. Ion - Ion Interactions in the Gas Phase top Dipole Moment Let's go back to that first ion pair which was formed when the positive ion and the negative ion came together.