The ion-dipole force is an intermolecular attraction between an ion and
a polar molecule.
LEARNING OBJECTIVE [ edit ]
Define ion-dipole force.
KEY POINTS [ edit ]
An ion-dipole interaction occurs between a fully charged ion and a partially charged dipole.
The strength of the ion-dipole force is proportionate to ion charge.
An ion-induced dipole interaction occurs between a fully charged ion and a temporarily charged
dipole. The temporary dipole is induced by the presence of the ion.
TERMS [ edit ]
ion-dipole forces
An electrostatic interaction involving a permanent dipole in onemolecule and an ion.
ion
An atom or group of atoms bearing an electrical charge, such as sodium and chlorine in table salt.
ion-induced dipole force
An electrostatic interaction involving a temporary dipole in one molecule and a permanently
charged ion.
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Ion-Dipole Force
Ion-dipole and ion-induced dipole forcesoperate much like dipole-dipole and induced dipoledipole interactions. However, ion-dipole forces involve ions instead of solely polar molecules.
Ion-dipole forces are stronger than dipole interactions because the charge of any ion is much
greater than the charge of a dipole; the
strength of the ion-dipole force is
proportionate to ion charge. Ion-dipole
bonding is also stronger than hydrogen
bonding. An ion-dipole force consists of an
ion and a polar molecule aligning so that
the positive and negative charges are next
to one another, allowing for maximum
attraction.
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Ion-dipole forces
Ion­dipole forces are generated between polar water molecules and a sodium ion. The oxygen atom in
the water molecule has a slight negative charge and is attracted to the positive sodium ion.
Theseintermolecular ion­dipole forces are much weaker than covalent or ionic bonds.
Ion-Induced Dipole Force
An ion-induced dipole force occurs when an ion interacts with a non-polar molecule. Like a
dipole-induced dipole force, the charge of the ion causes a distortion of the electron cloud in
the non-polar molecule, causing a temporary partial charge. The temporary partially charged
dipole and the ion are attracted to each other and form a fleeting interaction.