9.4. Intermolecular Forces http://www.ck12.org
Adipole-dipole forcecan be seen when two polar molecules interact with one another. The partial positive region
of one molecule will be attracted to the partial negative region of an adjacent one. Because both charges are partial
(less than a full charge), these interactions are weaker than those involving ions. An example of a dipole-dipole
interaction between two molecules of HCl is shown in theFigure9.17.
FIGURE 9.17
Dipole-dipole interactionsIon-Dipole Interactions
An ion-dipole interaction involves the attraction between a fully charged entity and a polar molecule. Both cations
and anions can participate in this type of bonding. A cation will be attracted to the partial negative portion of the
polar molecule, while an anion will interact with the partial positive region.
FIGURE 9.18
Polar molecules.The interaction of sodium and chloride ions with water is one example of an ion-dipole interaction:
The positive sodium ions are attracted to the partial negative portion of the water molecule (the red oxygen atoms),
while the negative chloride ions interact with the partial positive hydrogen portion (the blue atoms). Because one of
the bonding partners has only a partial positive or negative charge, these forces are somewhat weaker than ion-ion
interactions.