Hybridization of SnCl3 -

  1. I just had my exam today, so I had this question that is, what is the type of hybridization which occurs in SnCl3 - , my answer is sp2 hybridization because I thought that the last electron left wouldn't be hybridized. Am I correct?
     
  2. jcsd
  3. DrDu

    DrDu 4,420
    Science Advisor

    Hybridization is not an observable property of an atom, so this question makes little sense.
    More appropriate would be to ask with which kind of assumed hybridization would best fit the observed bond properties. Normally it makes little sense to consider hybridization beyond second row atoms as the size of s and p orbitals is becomes too different and the energy from bond formation doesn't make up for the propagation. So the best description would probably one where there is no hybridization, the free electron pair fills the s orbital and the bonding is due to the p orbitals, only.
     
  4. hmmm, let me quote the whole question to avoid any miscommunication.
    Tin (Sn) is an element of Group 14. What type of hybrid orbitals would tin use in SnCl3 (-1)

    A. sp
    B. sp2
    C. sp3
    D. sp3d

    I'm not sure if this changes anything but I hope there's an answer to this.

    PS: one more question
    For the hydrogen atom, the electron transition with the longest wavelength is

    A. n5 to n4
    B. n7 to n 6
    C. n6 to n1
    D. n2 to n1

    My friends say the answer should be B because the energy released when the electron moves from n=7 to n=6 is the smallest, thus the frequency is the smallest, and the wavelength is the longest.

    However I did a quick check on the internet, it seems most the answer given were D.

    Am I overlooking something important?
     
  5. I think it should be sp3. 2 paired electrons in the s orbital and 3 unpaired electron in p orbital used for bonding
     
  6. wouldn't that be 5 valence electrons when there's only 3 chlorine attached and the charge is negative 1
     
  7. DrDu

    DrDu 4,420
    Science Advisor

    Answer to the second question is D as you corretly said. The first question doesn't exactly rise my confidence in the school system of your country.
     
  8. Yes, and I would like to add that the majority of my country's people would agree with you. The country is going through brain drain, there's no helping it.

    Anyhow, can you give a brief explanation as to why the answer is D? Because I remember the difference of frequency between two energy levels decreases as it goes higher up, so the frequency produced for answer B should much lower than D.
     
  9. Borek

    Staff: Mentor

    Strange, I would expect B to be correct as well (for the hydrogen question).
     
  10. Taking a look at a model of SnCl3- (http://ce.sysu.edu.cn/echemi/inocbx/ic3/Sn/SnCl3-.html) it looks like it can be described with an hybridization. If the free electron filled the s orbital and the bonding were due to the p orbitals, wouldn't the bond angles be closer to 90 degrees?
     
  11. DrDu

    DrDu 4,420
    Science Advisor

    I am deeply sorry. I wanted to write "B is correct". Confounded the letters.
     
  12. DrDu

    DrDu 4,420
    Science Advisor

    According to crystal structures of salts containing the anion (e.g. K[SnCl_3].KCl.H2O), the bond angle found is indeed very close to 90 degree, e.g. 87.7 and 90.8 degrees for the salt mentioned.
    See: http://dx.doi.org/10.1016/0022-1902(62)80247-4
    Similar conclusions are found from IR or Raman spectroscopy in the solution:
    http://www.springerlink.com/content/xw4733261885q755/
     
  13. Is there any way to find this hybridization without any actual spectroscopy or such experiments? I mean, can something like the electronic configuration be used? After all, the OP was asked this for in a theoretical manner.
     
  14. DrDu

    DrDu 4,420
    Science Advisor

    My general advice is never to invoke hybridization when you are not forced to do so, especially not in main group compounds beyond the second row.
    Keep it simple!
    I gave a theoretical justification in post #2.
    Even in compound like water and NH3 little is gained in assuming hybridized orbitals.
    Also bond angles aren't a good argument in general. After all, there is no physical law why orbitals should line up 100% for optimal bonding.
     
  15. From post #2...

    I'm not sure I understand that properly. You say, the energy from bond formation doesn't make up for the propagation, which propagation is that?

    Thanks for the reply :smile:

    But the last statement puts me into confusion again. Bond angles do indicate the structure where the molecule is in maximum stability which every molecule is trying to attain, right? So orbitals should pretty much line up like that, I believe. Wasn't hybridization brought in to explain this, in the first place?
     
  16. DrDu

    DrDu 4,420
    Science Advisor

    I mean the energy necessary to lift e.g. an s electron to a p electron before hybridization. I confused promotion with propagation, sorry.
     
  17. Aha! Did some more reading into it, and I get it now. Thanks :smile:
     
  18. Yes, there is a way within a theoretical framework. Count all of the electrons, etc..., create your Lewis structure, and then count the number of electron domains, from there you'd get your molecular geometry. Within this case, there is a lone pair of electrons on the tin atom, but it is also a tetrahedral molecule (electron-pair geometry), however, its molecular geometry is trigonal pyramidal, so the hybridization for tetrahedral generally is sp^3.

    Sometimes, for instance in general chemistry, or organic chemistry, you can get the hybridization on that alone, however, there are instances where a molecules geometry won't exactly match up to its hybridization so knowing how to draw and deduce the sigma/pi - bonds, and knowings vesper theory would be more paramount than simply going on the "status-quo" so to speak. But within his course and this question, it is simply trying to test him on a more basic level of understanding.
     
  19. Gotcha. Thanks for the explanation!
     
  20. DrDu

    DrDu 4,420
    Science Advisor

    up to here, that is plain VSEPR theory.

    This has not the least scientific basis. Can you give a serious reference (I don't mean a high school text book) for this claim?
     
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