There are several types of van der Waals attraction : dipole/dipole, dipole/induced-dipole and spontaneous-dipole/induced-dipole.The spontaneousdipole/induced-dipole attractions are also known as London dispersion forces. LDF are surprisingly strong but are only short range forces e.g. surface of neutral molecules or inert gases. All molecules have LDF and strength increases with the size/surface area of the molecule. In case of halogens, \(\mathrm{LDF}\) increases as \(\mathrm{F}_2 < \mathrm{Cl}_2 < \mathrm{Br}_2 < \mathrm{I}_2\).