Summary:
- Van der Waals forces are the weakest intermolecular force and consist of dipole-dipole forces and dispersion forces.
- Dispersion forces are strongest for iodine molecules because they have the greatest number of electrons.
- The relatively stronger forces result in melting and boiling points which are the highest of the halogen group.
- These forces are strong enough to hold iodine molecules close together in the solid state at room temperature.
- Bromine, chlorine, and fluorine are gases, whose molecules are much further apart from one another.
- Interactions between non-polar molecules depend on the degree of electron fluctuation.