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2c-2e and 3c-4e bonds

  1. May 9, 2014 #1

    utkarshakash

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    1. The problem statement, all variables and given/known data
    Which of the following compounds contains both 2c-2e bond and 3c-4e bond?
    A) Be2Cl4 B) B2Cl4 C) (SnCl2) D) both A and C


    3. The attempt at a solution

    For 3c-4e bond, there must be 3 atoms present. So correct option should be C but the answer is D.
     
  2. jcsd
  3. May 9, 2014 #2

    AGNuke

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    Check the structure for Be2Cl4. You'll see.
     
  4. May 9, 2014 #3

    Qube

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    By 3c-4e do you mean 3 carbon 4 electron bond?
     
  5. May 9, 2014 #4

    utkarshakash

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    I'm not sure if I correctly understand the term "3c-4e" but I guess it must have 3 centres. Can you please explain what's that?
     
  6. May 9, 2014 #5

    AGNuke

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    In Be2Cl4, the two Be atoms are bridged by two Cl atoms. So, if you consider a Be-Cl-Be bridge, the Cl originally belongs to one of the Be atoms, thus accounting for a bond pair in the bridge. But that Cl atom donates its electron pair to the other Be atom so as to fill its empty orbitals, accounting for the other pair in the bridge.
     
  7. May 10, 2014 #6

    utkarshakash

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    OK. So why is it called 2c-2e and 3c-4e bond?What do these terms mean in general?
     
    Last edited: May 10, 2014
  8. May 10, 2014 #7

    AGNuke

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    Bonds are made by electrons, and bonds anchor the "centres". It is just some terminologies people like to come up with. If there are two atoms bonded by 2 electrons (a single bond), it is 2c-2e bond. If the overall bond is connecting 3 atoms and 4 electrons are playing the role of bonding, it is simply 3c-4e bond.
     
  9. May 10, 2014 #8

    utkarshakash

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    Thanks for explaining so nicely.
     
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