1
$\begingroup$

By what I've read, an ion-induced dipole attraction is a weak attraction that results when the approach of an ion creates a dipole in a non-polar atom or in a non-polar molecule by disturbing the arrangement of electrons in the non-polar species. So this is a dispersion/van-der-Waal force, I believe?

On the other hand, an ion-dipole attraction is a weak attraction that results when the approach of an ion interacts with the dipole in a polar atom or in a polar molecule. And so this wouldn't be a van-der-Waal force would it?


If what I said above happens to be true, does the same apply with dipole-induced dipole forces and just dipole-dipole forces?

In this scenario, a dipole-induced dipole attraction would be a weak attraction that results when the approach of an dipole (polar covalent bond) creates a dipole in a non-polar atom or in a non-polar molecule by disturbing the arrangement of electrons in the non-polar species. So this is a dispersion/van-der-Waal force too, right?

And a dipole-dipole attraction would be a weak attraction that results when the approach of an dipole that already exists in a polar bond attracts with another dipole in another polar atom or in polar molecule.

$\endgroup$
1
$\begingroup$

It is useful to note the definition of a van der Waal force: weak electric forces attracting neutral molecules to each other in gas thus causing a gas to deviate from an ideal gas.

So, there are three types of these forces

  1. Dipole-dipole force

  2. Dipole-induced dipole force

  3. London dispersion force

It becomes clear that forces involving ions do not fit van de Waals forces as the molecules involved must be neutral.

An ion-induced dipole force is not a dispersion force, either (as dispersion forces are a subset of van der Waals), and with ion-dipole forces, ion-induced dipole forces have a category of it's own

A dipole-induced dipole force is a van der Waal force but not a dispersion force

$\endgroup$
  • $\begingroup$ So what exactly is a London Dispersion force? I've been reading that it is sort of like a "Induced Dipole-Induced Dipole" interaction, where if neutral atom "x" is induced by a permanent dipole, then neutral atom "y" which next to "x" also gets induced by "x's" temporary dipole. Then neutral atom "z" gets induced by "y's" temporary dipole. Kind of like a chain reaction? If not, then what is it? $\endgroup$ – Aniket Dec 29 '16 at 20:01
  • $\begingroup$ An asymmetric distribution of electrons by chance can cause a temporary dipole, causing a slight positive and slight negative end, and the London Dispersion Forces involves the attraction of such atoms with dipoles. So it is an induced dipole-induced dipole, but not by the mechanism you described $\endgroup$ – Copper Dec 29 '16 at 22:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.