There are three types of van der Waals Attraction: Dipole/Dipole attraction in which molecules with permanent dipole moments interact with each other so that the dipoles line up "end-to-end" and which at temperatures below the materials melting point show long range order and crystal structure. Dipole/Induced-Dipole Attraction: Molecular dipoles are able to induce weak dipoles in adjacent non-polar species. London Force Attraction: The very fact that it is possible to liquefy helium and the other Group VIII gases demonstrates that there must be some type of inter-atomic attraction taking place, known as the "London force". For more information look in the Chemogenesis
webbook sections on Lewis
acids and Lewis bases and the Lewis
acid/base interaction matrix.