London (dispersion) force

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Monica Soliman 3F
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Joined: Wed Sep 30, 2020 9:57 pm

London (dispersion) force

Postby Monica Soliman 3F » Mon Nov 09, 2020 1:10 pm

In the lecture today, Professor Lavelle mentioned dispersion, however, I still do not quite understand it. Can someone explain it to me? And how would you know which molecules exhibit the London force?

Ria Nawathe 1C
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Re: London (dispersion) force

Postby Ria Nawathe 1C » Mon Nov 09, 2020 1:27 pm

London dispersion forces are induced dipole-induced-dipole interactions. Basically, when non-polar molecules collide their electron densities are shifted, forming a temporary delta negative and delta positive side. This induces the neighboring molecule to form a temporary dipole as well and produces a temporary attractive force between the 2 induced dipoles.

Lisa Seidl 3H
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Re: London (dispersion) force

Postby Lisa Seidl 3H » Mon Nov 09, 2020 1:27 pm

So this is the same thing as an Induced Dipole - Induced Dipole interaction where the two molecules interact with each other and thereby become induced dipoles creating partial negative and positive charges on opposite sides that fluctuate.

Samantha Pedersen 2K
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Re: London (dispersion) force

Postby Samantha Pedersen 2K » Mon Nov 09, 2020 2:32 pm

When molecules collide, one atom repels the electrons away from another, creating a partial positive charge on the second atom. The partial positive charge on that atom creates a partial negative charge on the atom that it is bonded to (because the electrons are repelled away from the first atom toward the atom that it is bonded to). These partial positive and partial negative charges then start to influence the charges of atoms in molecules around them.

These London dispersion forces are actually present in all molecules! I hope this helps!

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