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Coulomb's force in atoms and effect on dipoles

  1. Apr 21, 2014 #1
    I've had this question for awhile. I asked my ochem professor and he didn't know how to answer it. My physics professor answered it but still left me with questions.

    In physics, the force of two charged particles is shows by Coulombs eq: F= k* q1 * q2/ r^2.

    My question is, why do dipoles even exist, if like charges repel? Take oxygen, for example. It has 8 protons, and needs 8 electrons to have a net charge of 0. As we see, when O bonds with H, it partly 'steals' the electrons from H.

    Why wouldn't O, or any other molecule for that matter, just be satisfied with the e electrons that it gets from a bond? Why do electronegative atoms need to take EVEN MORE e? I feel that, by coulombs law, the extra e would be repelled by the other electrons.

    My physics proff said that the electrons are attracted to O because of the difference in radii between the Oxygen atom, its electrons, and the electrons of the H.

    That bring me to my same question again, though. Why would all of the electrons hang around on one side of oxygen? Things are more stable when charges are delocalized, so why wouldn't Oxygen delocalize the negative dipole it amasses?

    I've been thinking about this for awhile, and my whole view on electronegativity has been shaken. Any help would be appreciated!!!
  2. jcsd
  3. Apr 22, 2014 #2


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    Polar molecules have a non-symmetric structure, so the electron cloud "has trouble" being everywhere at once due to the lack of symmetry ... hence water has a dipole moment.

    Why doesn't it collapse? Because the forces holding the molecule together are stronger than the net force of the shielded dipole.

    To work out the details from fundamental principles is difficult - something that may be a suitable PhD research topic in physical chemistry.
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