Understanding First Ionization Energy for Diatomic Gases

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SUMMARY

The discussion centers on the concept of first ionization energy for diatomic gases, specifically molecular hydrogen (H2). It is established that ionization energy refers to the energy required to remove an electron from isolated atoms rather than diatomic molecules. The second ionization energy for molecular hydrogen does not exist in the classical sense, as removing both electrons results in the dissociation of the molecule into two protons and one electron, rather than forming a stable ion. Participants clarify that while energy is required to remove the second electron, it is not appropriate to label this as "ionization" energy.

PREREQUISITES
  • Understanding of ionization energy concepts
  • Familiarity with molecular structure and bonding
  • Knowledge of dissociation energy in molecular chemistry
  • Basic principles of atomic versus molecular ionization
NEXT STEPS
  • Research the concept of ionization energy in diatomic molecules
  • Study the dissociation energy of molecular hydrogen (H2)
  • Explore the differences between atomic and molecular ionization energies
  • Investigate the implications of electron removal on molecular stability
USEFUL FOR

Chemistry students, educators, and researchers interested in molecular ionization processes and the behavior of diatomic gases in chemical reactions.

Samson4
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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?
 
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Always the isolated atoms.
 
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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.
 
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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?
 
Molecular hydrogen has just two electrons per molecule. There is no double ionized molecule.
 
Then what is second ionization energy?
 
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.
 
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Samson4 said:
Then what is second ionization energy?
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.
 
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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