what are london and dipole-dipole forces???
Dispersion Forces or London Forces are the forces of attraction between two temporary dipoles It occur between atoms or non-polar molecules.
Atoms or non-polar molecules have no dipole moment as they are electrically symmetrical. However, for some reason, momentarily an atom or non-polar molecule becomes electrically unsymmetrical. As a result, instantaneous dipole is developed on that atom for a very short time. This instantaneous dipole induces dipole on another atom close to it.
Dipole-Dipole interaction or Dipole-Dipole Forces
* Forces between molecules possessing permanent dipole
* Increase with decrease in distance
* For stationary polar molecules, Eā 1/r3
* And for rotating polar molecules, E ā 1/r6
Where, E = Interaction energy and r = Distance between the polar molecules
* For polar molecules, total intermolecular forces = Dipole-dipole forces + London forces
* Dipole-dipole interaction between two HCl molecules: