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Stability of Sulfides

  1. Jan 11, 2015 #1

    Qube

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    1. The problem statement, all variables and given/known data

    The attempt at a solution

    1) Is the above excerpt describing pi-backbonding? It seems to be describing some form of backbonding because the electron density is moving away from the positively charged metal cation (rather unexpected based on superficial Columbic analysis).

    2) Is pi-backbonding more favorable for metals in a low rather than a high oxidation state because such metals still have substantial electron density that needs to be stabilized - and preferably stabilized by something more electronegative than a metal?

    3) Metal d-orbitals overlap with p or d-orbitals of the non-metal. How does this work? I always see diagrams such as these:

    dj038.png

    Is the overlap between the metal d-orbital and non-metal p-orbital as poor as depicted? Are the d-orbitals really at a 45 degree angle relative to the p-orbital?

    3b) Why does there seem to be 4 bonds in the carbon monoxide ligand in the above diagram? Shouldn't there be instead 2 lines between C and O not 3 lines and two aligned p-orbitals? (Probably being a bit nit-picky here).

    4) How well is the above excerpt written? I feel that two improvements could be made:

    A) The passage seems to imply that Bronsted acidity and basicity do not depend on the corresponding base or acid. Wrong implication. HCl in HBr solvent won't be a strong acid.

    B) Why electron density might just "drift" to the non-metal could be explained explicitly. I.e. electronegativity.
     
    Last edited: Jan 11, 2015
  2. jcsd
  3. Jan 11, 2015 #2

    Bystander

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    It's a little hard to say what it's trying to describe.
    If one really has to think in terms of "backbonding," it's more favorable for a "softer" ion.
    This is analogous to p-pi -- p-pi bonding at a higher level of occupation; the d orbitals include higher probabilities of finding electrons close to an atomic nucleus than do the s and p orbitals, making "delocalization" between a pair of nuclei with accessible and/or occupied d orbitals advantageous.
    Someone is mixing depictions of pi-bonding with conservation of line drawings of tetravalent carbon.
    You seem unimpressed. Check the front end of the book for the author's/authors' credentials; there's a very good possibility you will find "M. Ed." and/or "Ed. D." listed.
     
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