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Homework Help: What is the binding energy in NaCl?

  1. Oct 18, 2011 #1
    1. The problem statement, all variables and given/known data
    Each Na atom transfers 1/6 of an electron, on average, to each Cl atom. Estimate the binidng energy of the ionic bonds in NaCl.


    2. Relevant equations



    3. The attempt at a solution
    The answer says to use k*q1*q2 / r, where k is the electric constant, q1 and q2 are the charges, and r is the separation between the charges.

    So it gives k*(1/6)e*e / r.

    I'm wondering what would happen if it were a different atom. In NaCl, Na has a charge of +1 and Cl has a charge of -1. If I wanted to calculate the binding energy of something with charges that weren't necessarily 1, how would this change?
     
  2. jcsd
  3. Oct 19, 2011 #2

    Borek

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    Staff: Mentor

    This is based on a simple coulomb interactions between point charges.
     
  4. Oct 19, 2011 #3
    I know. It's the charges of the ions I'm unclear on. I just wanted to know what the answer would look like if the question was about, say MgO instead of NaCl.
     
  5. Oct 19, 2011 #4

    Borek

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    Staff: Mentor

    MgO would mean charges +2 and -2. 1/6th is just effect of the geometry, so in the case of MgO I would expect 2/6th.
     
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