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Unpaired electronS

  1. Nov 10, 2006 #1

    quasar987

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    In Reif's thermo book, one can read

    "Consider a substance which contains n magnetics atoms per unit volumes and which is placed in an external magnetic hield B. Assume that each atom has spin 1/2 (corresponding to one unpaired electron) and an intrinsic magnetic moment of [itex]\mu[/itex]."

    He makes it sound like it's possible to have more than one unpaired electron. Is this so? I interpret "unpaired" as "there is one electron in a state r and spin up (resp. down) such that there are no electrons in state r with spin down (resp. up). But as soon as you add one more electrons, it will get in state r with spin down (resp. up) so there are no more unpaired electrons. Hence it's impossible to have more than 1 unpaired. Is this how it work?
     
  2. jcsd
  3. Nov 10, 2006 #2
    I'm not sure if I understand you completely but... look up Hund's rules. An atom can have more than one unpaired electron. They're in different angular momentum states though.
     
  4. Nov 10, 2006 #3

    dextercioby

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    Surely if you've ever studied chemistry you might know that "unpaired electrons" occur when writing the electron configurations for various atoms. For instance, the Carbon atom has 2 unpaired electrons, N has 3, etc.

    Daniel.
     
  5. Nov 10, 2006 #4

    quasar987

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    What is an unpaired electron then?

    I've said what I remember from chemistry. You fill up the states two by two since an up and a down can occupy the same state. If there is an even number of electrons, there there is no unpaired electrons; if the number is odd there is one.
     
  6. Nov 13, 2006 #5

    dextercioby

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    Nope, Hund rules make it that the Carbon atom which had 6 electrons altogether have the configuration

    1s2 2s2 2p2

    , but the 2 electrons in the "p" orbital are uncoupled (i.e. in different total angular momentul states), meaning that the spins are not antiparallel in the same orbital (p_{x}), but are alligned & parallel in the 2 orbitals:2p_{x} & 2p_{y}, rendering the total spin 1, instead of 0.

    Daniel.
     
  7. Nov 13, 2006 #6

    quasar987

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    Ah, I see, thank you.
     
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