Editing Intermolecular force (section)

==Dipole–dipole and similar interactions {{anchor|Dipole-dipole interactions}}==

Dipole–dipole interactions (or Keesom interactions) are electrostatic interactions between molecules which have permanent dipoles. This interaction  is stronger than the London forces but is weaker than ion-ion interaction because only partial charges are involved. These interactions tend to align the molecules to increase attraction (reducing [[potential energy]]). An example of a dipole–dipole interaction can be seen in [[hydrogen chloride]] (HCl): the positive end of a polar molecule will attract the negative end of the other molecule and influence its position. Polar molecules have a net attraction between them. Examples of polar molecules include [[hydrogen chloride]] (HCl) and [[chloroform]] (CHCl<sub>3</sub>).

:{{Dipole-dipole-interaction-in-HCl-2D}}

Often molecules contain dipolar groups of atoms, but have no overall [[Electric dipole moment|dipole moment]] on the molecule as a whole. This occurs if there is symmetry within the molecule that causes the dipoles to cancel each other out. This occurs in molecules such as [[tetrachloromethane]] and [[carbon dioxide]]. The dipole–dipole interaction between two individual atoms is usually zero, since atoms rarely carry a permanent dipole.

The Keesom interaction is a van der Waals force. It is discussed further in the section "Van der Waals forces".

===Ion–dipole and ion–induced dipole forces===

Ion–dipole and ion–induced dipole forces are similar to dipole–dipole and dipole–induced dipole interactions but involve ions, instead of only polar and non-polar molecules. Ion–dipole and ion–induced dipole forces are stronger than dipole–dipole interactions because the charge of any ion is much greater than the charge of a dipole moment. Ion–dipole bonding is stronger than hydrogen bonding.<ref>{{Cite book|title=Chemistry: A Molecular Approach| vauthors = Tro N |publisher=Pearson Education Inc|year=2011|isbn=978-0-321-65178-5|location=United States|pages=466}}</ref>

An ion–dipole force consists of an ion and a polar molecule interacting. They align so that the positive and negative groups are next to one another, allowing maximum attraction. An important example of this interaction is hydration of ions in water which give rise to [[Hydration energy|hydration enthalpy]]. The polar water molecules surround themselves around ions in water and the energy released during the process is known as hydration enthalpy. The interaction has its immense importance in justifying the stability of various ions (like Cu<sup>2+</sup>) in water.

An ion–induced dipole force consists of an ion and a non-polar molecule interacting. Like a dipole–induced dipole force, the charge of the ion causes distortion of the electron cloud on the non-polar molecule.<ref name=Michael-Blaber-1996>{{cite web | vauthors = Blaber M | date = 1996 | url = http://www.mikeblaber.org/oldwine/chm1045/notes/Forces/Intermol/Forces02.htm | title = Intermolecular Forces | work = mikeblaber.org | access-date = 2011-11-17 | archive-date = 2020-08-01 | archive-url = https://web.archive.org/web/20200801205131/http://www.mikeblaber.org/oldwine/chm1045/notes/Forces/Intermol/Forces02.htm | url-status = usurped }}</ref>