The three major types of intermolecular interactions are dipole–dipole interactions, London dispersion forces (these two are often referred to collectively as van der Waals forces), and hydrogen bonds.

NH3 is polar because it has 3 dipoles that do not cancel out. Each N-H bond is polar because N is more electronegative than H. NH3 is overall asymmetrical in its VSEPR shape, so the dipoles don’t cancel out and it is therefore polar.

The London dispersion force is the weakest intermolecular force. The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles.

Key Takeaways: Intermolecular Forces Intermolecular forces are weaker than intramolecular forces. Examples of intermolecular forces include the London dispersion force, dipole-dipole interaction, ion-dipole interaction, and van der Waals forces.

Types of Intermolecular Forces

• Dipole-Dipole Interactions. Dipole-dipole interactions are attractive forces among polar molecules.
• Ion-Dipole Interactions.
• Ion Induced Dipole Interactions.
• Dipole Induced Dipole Interaction.
• Dispersion Forces or London Forces.

London dispersion forces

Intermolecular forces are mainly of two types, repulsive forces and attractive forces. The intermolecular forces of attraction are also known as Van der Waals forces.

Examples of Dipole-Dipole Interactions Another example of a dipole–dipole interaction can be seen in hydrogen chloride (HCl): the relatively positive end of a polar molecule will attract the relatively negative end of another HCl molecule.

Carbon dioxide does not have dipole-dipole forces due to symmetry of the dipoles found in the molecule as a result of the polar bonds. Carbon dioxide is not a polar molecule despite its polar bonds. Carbon dioxide also does not have hydrogen bond forces because it is a nonpolar molecule.

Carbon dioxide does not have a permanent dipole moment; that is a fact. Therefore it is considered by chemists to be a nonpolar molecule, irrespective of the polarity of any single constituent bond. This is the accepted definition of “nonpolar”.

CO2 has polar bonds (O is much more electronegative than C) but the polar bonds ARE symmetrically opposite to one another so CO2 is not a polar molecule and does not have permanent dipole-dipole interactions. The strongest type of intermolecular forces are called hydrogen bonds.

In CH2Cl2, the Cl pulls much more on the Carbon’s electrons (since it has higher electronegativity) than the Hydrogens, which sets up a dipole moment (i.e. polar).

CH2Cl2 is a polar molecule due to its tetrahedral geometrical shape and difference between the electronegativity of Carbon, Hydrogen and Chlorine atoms. This develops a dipole moment across C-Cl and C-H bonds and the entire molecule results in a net 1.67 D dipole moment.

Carbon tetrachloride,CCl4, has a net dipole moment of zero. Even though each of the four C-Cl bonds is distinctly polar, the resultant moment of any three of them is equal in magnitude but opposite in direction to the moment due to the fourth one. So, the molecule’s net dipole moment is zero, and it is non-polar.