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Coulomb Energy

  1. Feb 3, 2013 #1
    The ionization of potassium is 4.34 eV; the electron affinity of iodine is 3.06 eV. At what separation distance will the KI molecule gain enough Coulomb energy to overcome the energy needed to form the [itex]K^+[/itex] and [itex]I^-[/itex] ions?

    I'm looking at the solution to this problem and I'm not understanding how they get the Coulomb energy. Is it just the
    E_n=\frac{-Z^2 (13.6eV)}{n^2}
    equation? I'm not getting the same numbers they're getting so I think I'm confused on the definition of Coulomb energy. Can someone clarify it for me. I understand the Coulomb repulsion/attraction is what I've seen over and over again from electrostatics...but I don't see how to tie that into this problem. Specifically because I don't know the radius of the particular ions.

    They're getting values of 3.06 and 4.34 eV

    Please and Thanks.
  2. jcsd
  3. Feb 3, 2013 #2
    Ugh, nevermind. My brain is fried...I figured it out.
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