Delocalization in metals and conjugated systems

  1. Hi Fellow Members,
    I am a bit confused about delocalization concept. Since, in organic chemistry we have been told that delocalization only exits between conjugated systems but in inorganic chemistry there is delocalization of electrons in metals with no double bonds. Isn't it confusing, is there a difference between both delocalization. Please help me out.

    Thanks
    Faisal
     
  2. jcsd
  3. Borek

    Staff: Mentor

    Delocalization means electron is not bounded to an atom, but can travel much further.

    It is possible in conjugated pi systems, it is possible in metals. These are very different systems, but the idea remains the same.
     
  4. My limited understanding of each phenomenon is that in a conjugated system the ground electron configuration leads to delocalization whereas in a conductor the valence electron(s) need(s) to overcome the band gap in order to delocalize.
     
  5. Borek

    Staff: Mentor

    Not that I feel confident about these things either, but there is no band gap in conductors, that's why they are conductors.
     
  6. Could be, I will do some reading later in the evening. I thought that conductors simply have very small band gaps which are populated at reasonable temperatures according to the Boltzmann distribution. Maybe that is just semantics?

    EDIT: Sorry, Borek is correct. Conductors have overlap of valence and conduction bands. See: http://hyperphysics.phy-astr.gsu.edu/hbase/solids/band.html
     
    Last edited: Dec 2, 2013
  7. Borek

    Staff: Mentor

    You don't have to be sorry about me being correct :tongue2:

    But I am wrong often enough to be happy when I get something right :wink:
     
  8. DrDu

    DrDu 4,353
    Science Advisor

    Delocalization always occurs when you can draw several equivalent resonance structures. In organic chemistry, this usually only happens for the pi system, although there are exceptions like e.g. CH5+.
    In metals, boron compounds etc. delocalization is more commonplace as metals tend to have more orbitals than electrons, so that more bonding possibilities become possible.
    What also matters, i the low electronegativity of metals. This allows for the possibility to include ionic resonance structures, so that not only compounds with alternating bonds will show delocalization.
     
  9. Ok, it means that lewis resonance structure represents only delocalization. bond breakage is only for representation. metal exists as a hybrid structure of lewis resonance structures. Delocalization in metal is due to the increased density of electron in metal. Please Let me know if I am correct.

    Thanks
     
  10. DrDu

    DrDu 4,353
    Science Advisor

    Yes, this is basically Pauli's resonating valence bond description of metallic bonding.
     
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