There exists the basic chemistry lesson with induced dipoles where the electron density of one atom changes causing a dipole to form and causing a cascading effect where other atoms adjacent to that polarized atom also become polarized.

How do those atoms lose their dipole if their wavefunction changes to "line up" with the dipole? Does a probabilistic event need to happen at the same time for all atoms in order to "lose" the dipole where the electron density goes back to its normal state?


1 Answer 1


The said lesson tends to oversimplify things to the point of getting them downright wrong. Atom dipoles do not line up with each other. They are way too weak for that. Should it be according to your description, they would indeed line up all in one direction and stay locked forever, much like magnetic particles in a magnet.

Now, I brought up the magnetic analogy because it is much better known than the similar electric phenomenon, called ferroelectricity. That's where your explanation is precisely right. Compounds that exhibit ferroelectric properties, once polarized, never lose their dipoles unless you force them to. But they constitute just a tiniest minority of all compounds.

What happens in the rest of them? Well, the molecules turn this way and that, atoms bounce and wiggle, spontaneous dipoles arise every now and then, only to vanish almost instantly. But the position where two neighboring dipoles are aligned in the same direction is energetically favorable, so they spend a little more time in this position than in the opposite. And that's what we call induced dipoles, dispersion forces, etc.

So it goes.


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