Fluctuating Dipoles

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Kyle Harvey 4F
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Joined: Sat Aug 24, 2019 12:17 am

Fluctuating Dipoles

Postby Kyle Harvey 4F » Sun Nov 10, 2019 8:23 pm

What does it mean when talking about fluctuating dipoles when there is fluctuating electron distribution?

Helen Struble 2F
Posts: 97
Joined: Sat Aug 24, 2019 12:17 am

Re: Fluctuating Dipoles

Postby Helen Struble 2F » Sun Nov 10, 2019 8:30 pm

Remember that electrons exist in a cloud around an atom. Though we can use probability and wave functions to get an idea of where they are likely to be, we can never know for sure where electrons are around the atom/molecule at any given moment. Occasionally, the electrons random motion around the atom/molecule will produce dipoles. Imagine if all the electrons happened to be on one side of the atom/molecule at a particular moment. At that instant, the molecule will have a slightly negative charge on the side where all the electrons are. This is the fluctuating, instantaneous dipole you describe.

Naji Sarsam 1F
Posts: 104
Joined: Sat Aug 17, 2019 12:18 am

Re: Fluctuating Dipoles

Postby Naji Sarsam 1F » Sun Nov 10, 2019 8:30 pm

Fluctuating dipoles becomes important when discussing induced dipole - induced dipole interactions.

A simplification of the premise is that electrons in an atom are always moving; they are not static. Thus, in molecules, electrons are still moving around their atoms in, essentially, random motion. Thus, sometimes due to random chance, the electrons of atoms in a molecule all move to one side of the molecule. Again, this happens totally by chance and for only split seconds. However, this imbalance of electron distribution does cause a temporary induced dipole in a molecule. This temporary dipole may influence the motion of electrons in another molecule--which must be very, very close--to cause a dipole. That is what causes induced dipole - induced dipole interactions.

JonathanS 1H
Posts: 101
Joined: Thu Jul 11, 2019 12:17 am

Re: Fluctuating Dipoles

Postby JonathanS 1H » Sun Nov 10, 2019 8:32 pm

Fluctuating dipoles and electron fluctuation refers to the random movement of electrons around an atom/molecule. This allows regions to become partially charged, which in turn causes regions of another molecule/atom to become partially charged. This causes attraction known as van der waals/induced dipole-induced dipole. There is essentially always fluctuating electrons around an atom.

Posts: 109
Joined: Thu Sep 26, 2019 12:18 am

Re: Fluctuating Dipoles

Postby alex_4l » Sun Nov 10, 2019 8:46 pm

I understand the concept of the fluctuating dipole due to the spontaneity of the electrons and their movement. However, how would this impact the way that we write out an example of the dipole on a test or a homework problem? Would it stay the same and we just have to know the concept or would we have to write out something different for it?

Juliet Stephenson 4E
Posts: 100
Joined: Wed Sep 18, 2019 12:21 am

Re: Fluctuating Dipoles

Postby Juliet Stephenson 4E » Sun Nov 10, 2019 8:48 pm

I don't think we would have to illustrate this very often. Maybe we might have to use partial charges like we do with hydrogen bonds. Hopefully we will get more examples in class.

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