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Relations between workfunction, ionization, redox and fermi

  1. Mar 16, 2015 #1
    My understanding so far, critique appreciated:

    [1] workfunction closely relates to reduction potential
    Since workfunction is about boundaries and chemical reaction are mostly happening at the boundaries between bulk material, Workfunction should have a direct correlation with reduction potential. for example if a Zinc ingot is more active in acid than an iron ingot then, that zinc block must have lower workfunction (easier to liberate an eletron)

    [2] ionization closely relates to fermi level
    I felt that, a gaseous single atom's most energetic electron's energy will probably not far from the energy of the top of fermi ocean in which gazillion of the same kind of atoms reside. so ionization energy (of the first electron) should be very related to 0 - FermiLevelEnergy.

    [3] Workfunction does not relate to fermi level that well...
    not sure why, crystal lattices and boundary condition probably play a role...?
     
  2. jcsd
  3. Mar 17, 2015 #2

    Simon Bridge

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    The workfunction is the minimum work you need to do to remove an electron from a solid to a point immediately outside the solid.
    The redox potential is a measure of the tendancy of chemical species to acquire electrons.

    The process of an atom acquiring an electron from a solid would involve both these concepts.
    You can check your example - does a zinc ingot have a lower workfunction than an iron ingot
    Can you come up with other examples?

    Ionization is the process by which atoms gain an unbalanced charge.
    The Fermi level is the max occupied energy state at zero absolute.
    At higher temperatures, the top occupied energy level can be higher.
    However, the ionization energy is measured from the ground-state ... so it would be related to the individual atom's Fermi level.

    None of the terms relate in a simple way.
    Lattices and boundary conditions certainly play a role.
     
  4. Mar 17, 2015 #3
    Hi Simon, Thank you very much for you reply again. Remember some guy asked a weird question of "E field and Flux D, which is more fundamental", that was me too =D. and yes, E was more fundamental.

    I made some revisions to my original post, to make it more precise..ish.

    when I say 2 quantities are "related", I do not mean a constant or formula can be used to convert one quantity into another.
    I mean more like: "when your sort a quantity from biggest to smallest, the other quantity should almost follow suit, not too many exceptions".

    [1] Workfunction should be closely related to "oxidation likelyhood" ( the likely hood of losing an electron in chemical reactions)
    this one might not be true, as oxidation may not involve just 1 reduction agent and 1 oxidation agent, in addition, it is more than 1 valence electrons are involved.

    When I check a table of workfunctions shown below, I didn't get too many surprises:

    Element vs Work Function(eV)
    Aluminum 4.08
    Beryllium 5.0
    Cadmium 4.07
    Calcium 2.9
    Carbon 4.81
    Cesium 2.1
    Cobalt 5.0
    Copper 4.7
    Gold 5.1
    Iron 4.5
    Lead 4.14
    Magnesium 3.68
    Mercury 4.5
    Nickel 5.01
    Niobium 4.3
    Potassium 2.3
    Platinum 6.35
    Selenium 5.11
    Silver 4.26-4.73*
    Sodium 2.28
    Uranium 3.6
    Zinc 4.3

    values Cadmium and Lead are kind unexpected, I thought those were less likely to react with acid. I knew Uranium was an exception, as f shells are trouble, I don't intend to understand them.

    [2] ionization ENERGY (just pulling one electron of one atom to potential 0) should be related to Fermi Level of a bulk of the same atom
    (fermi energy is the level filled up to @ T=0, fermi level here means 50% chance of occupation @ T = whatever)

    in your reply you emphasized on "fermi level of ONE atom". Which I agree, actually I think ionization energy should be equal to 0 - fermi-level-of-that-atom.

    I am imagining that for valence bounded materials, fermi level could be way out of wack compared to their single atom in gaseous state.
    But, for metals, the influence of lattice shouldn't be that great (my pure speculation), so the bulk material's fermi level should be related to its single atom's ionization energy.
     
    Last edited: Mar 17, 2015
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