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Homework Help: Valence Bond question (Chemistry)

  1. Nov 13, 2004 #1
    I'm working a problem with the BH3 molecule. Therefore boron is 1s^2 2s^2 2p^1, and using the hypotetical method, it forms hybird sp2 orbitals. Promoting an electron to get 1s^2 2s^1 2p^2.

    My question is that, it will form 3 bonding orbitals, one from the 1s and 2 from the 2p orbitals... what happends to the third 2p orbital? If I do an energy level diagram, do I have to list this orbital as a nonbonding one?

    I posted this on the chemistry forum, but decided to post it here because there are more people visiting this one.
  2. jcsd
  3. Nov 14, 2004 #2
    I don't know if you'd particularly list it as nonbinding or not, but yes, all the bonding when you have single bonds is done by hybrid orbitals (sp2); the leftover 2p orbital only has something to do if you have a double bond in the molecule. As it is, it'd just stick out perpendicular to the plane of the three sp2 orbitals.
  4. Nov 14, 2004 #3
    So, should I listed in the VB energy level diagram for the BH3 molecule? In case it ionizes, gaining electrons... would they go to this nonbonding orbital?
  5. Nov 14, 2004 #4
    If by the valence bond energy diagram you mean this kind of thing

    _ _ _ _
    _ _

    and so forth, then yes, you should list the remaining 2p (it's going to be slightly higher than sp since sp is a combination of s and p, after all) in the diagram - not because it plays or doesn't play a role in bonding necessarily, though, but just because these diagrams show all the orbitals you have. check and add up your electrons to figure out if the orbital is filled or not, though.
  6. Nov 14, 2004 #5
    Thanks Duarh, thank you very much for your help.
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