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London Forces, current, and boiling and melting points

  1. Sep 30, 2009 #1
    Alright, so I've posted this in physics forum not so long ago, but still haven't gotten any responses.

    Ok, so we know that the more electrons there are in the valence shell of an atom, the stronger the London Dispersion Forces are, and therefore, the compound will have a higher melting and boiling points.

    But now suppose electricity is being conducted through the object. Because it will have a smaller number of valence electrons (those are the charged particles that flow, creating electric current), would it be safe to assume that the London Forces would get weaker, and therefore, the overall sum of intermolecular forces would be less than the original, resulting in lower melting and boiling points?

    In other words, would it require less energy to break the intermolecular forces on an object that has an current passing through it?


    Though this up in chemistry class
    Pardon my grammar, just woke up
     
  2. jcsd
  3. Sep 30, 2009 #2
    Does anyone actually know the answer to that question? Or is this something new to the scientific world?

    :) I wish
     
  4. Sep 30, 2009 #3

    Ygggdrasil

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    Conductive materials like metals generally are not bound together by dispersion forces. The fact that electrons can flow between atoms means that the molecules' orbitals overlap and are therefore chemically bound. In this case, the dispersion forces will be much weaker than the actual chemical bonds.

    Applying an electric field to a system of particles that interact via dispersion forces would probably increase the intermolecular forces, however. The electric field would induce dipoles in the molecules and you could have dipole-dipole interactions rather than dispersion interactions.
     
  5. Oct 1, 2009 #4
    I'm currently studying a section on intermolecular forces. I don't know much about electric fields, but since you said this would induce dipoles, wouldn't this mean that an electric field would actually strengthen the bonds between the metal atoms, since dipole forces are much stronger than dispersion forces?
     
  6. Oct 1, 2009 #5

    chemisttree

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    Yep.

    Yggie-d wrote:
     
  7. Oct 1, 2009 #6
    Thank you all.
     
  8. Oct 2, 2009 #7

    Ygggdrasil

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    In metals, the primary interatomic force holding the atoms together is the overlap of the atomic orbitals of the metal atoms (which is much stronger than typical dipole-dipole interactions). Although I do not know how electric fields would affect these forces, if they did increase the strength of the bonds between metal atoms, it would not be by inducing dipoles to strengthening dipole-dipole interactions.

    This mechanism would, however, be valid in a gas (or possibly liquid) where the intermolecular forces are weaker.
     
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