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Bond length

  1. Feb 19, 2015 #1
    Arrange these bonds in order of increasing bond length.
    C-I, C-Br, C-Cl, C-F

    Is there a way to figure this out without drawing molecular orbital diagrams and determining the bond order?
     
  2. jcsd
  3. Feb 19, 2015 #2
    its been a while since chemistry, but wont electronegativity do it , shortest being carbon with the most electronegative (flourine)?
     
  4. Feb 19, 2015 #3

    Borek

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    What about radii of the atoms involved? Aren't they enough to predict the outcome? These are all very similar bonds, carbon-halogen, no need for any more advanced approach when you can safely solve the problem assuming "all other factors are being equal".
     
  5. Feb 19, 2015 #4
    The radii and the electronegativity follow the same pattern in this case, one is because of the other but its amazing how much you forget in a year (i can't remember off hand why size decreases as number increases accross a row, im sure with a little thinking I'd get it)

    but if either of s are right both of us are right in the context of your question and I'm pretty sure we are
     
  6. Feb 19, 2015 #5

    Borek

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    I am not convinced following electronegativity is a good idea. I can't think of good examples of molecules where the electronegativity is the only thing changing (or at least where all other changes are negligible) which is an important condition for such comparisons.
     
  7. Feb 19, 2015 #6
    you may be right, as I said its been a year and I can't get into my chemistry brain right now, but i'm sure electronegativity goes down with increasing radius so our answers would be the same in this context.

    personally I feel just looking at the size of the atoms isn't conceptually enough, it happens to work here but the haogens sharing with carbon in the first place cause it wants those electrons bad and carbon doesnt want to give them up.
    how bad the halogen wants them would be its electronegativity and changes with the halogen choosen
    how much carbon wants to keep them would be its electron affinity, and is constant

    sooo, how hard there pulled together should be to some degree a function of electronegativity right?


    like I said its been a minute and my brains in physics world atm. so any misinformation is possible and accidental
     
  8. Feb 19, 2015 #7

    Borek

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    In general it is not, but this is a very specific question.
     
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