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First ionization energy

  1. Nov 3, 2015 #1
    When looking at ionization energy charts; specifically for diatomic gasses, are we looking at the energy to take 1 electron from atomic or diatomic gasses?
     
  2. jcsd
  3. Nov 3, 2015 #2

    mfb

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    Always the isolated atoms.
     
  4. Nov 3, 2015 #3
    If it's for a diatomic gas, it is for a molecule of course. And it is different from the atomic ionization energy.
    And yes, it means (usually) energy to remove one electron. But it can be also energy to remove a second one and so on.
     
  5. Nov 3, 2015 #4
    That's what I figured. What I don't get is why I can't find the second ionization energy of molecular hydrogen. I've searched everything I can think of. Would it be the 104 kcal per mole bond dissociation energy?
     
  6. Nov 3, 2015 #5
    Molecular hydrogen has just two electrons per molecule. There is no double ionized molecule.
     
  7. Nov 4, 2015 #6
    Then what is second ionization energy?
     
  8. Nov 4, 2015 #7

    mfb

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    It does not have one in the classical sense. You can give the energy needed to completely split it apart (to two protons and an electron), but that is not a regular ionization.
    If you don't find that number directly, take the dissociation energy and add the hydrogen atom ionization energy.
     
  9. Nov 4, 2015 #8
    You just said that you cannot find this second ionization energy, didn't you?
    If you remove both electrons you don't have a molecule anymore. So there is no ion to talk about.
    There is this energy, to remove the second electron, but it won't be proper to call it "ionization" energy.
     
  10. Nov 4, 2015 #9
    Thank you for your help everyone.

    Mfb, that last bit was gold.

    Nasu, wouldn't there be 2 ions to talk about?
     
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