I was reading about the Pauli exclusion principle and this question occured to me about the electron. It can be +1/2 or -1/2 spin. And usually atoms outside stars (where it is cool enough to attach electrons) seem to have their orbitals filled with enough electrons to appear neutral. So I assume there are similar number of electrons with +1/2 and -1/2 spin, and they are quite evenly mixed. Is this true/generally true? Is there no assymetry like in matter antimatter?

  • $\begingroup$ Electrons have two spin quantum numbers, $S=1/2$ and the second is the azimuthal/projection/magnetic quantum number with $s_m=\pm 1/2$ . The electron with spin $S=1/2, s_m=1/2$ is the same as that with $S=1/2, s_m=-1/2$ unless you put the electron (or other spin particle say a proton) in a magnetic field then the energy levels split and one rises and one falls in energy by an equal amount but now by Boltzmann distribution the numbers of $s_m=1/2$ is no longer equal to that with $-1/2$. This forms the basis of EPR spectroscopy and NMR with protons etc. $\endgroup$
    – porphyrin
    Nov 1, 2022 at 16:43
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    $\begingroup$ Spin of electron as a particle is 1/2, no plus or minus. These signs are only to symbolise that these moments are opposite if two electrons "are in" one orbital. $\endgroup$
    – Mithoron
    Nov 1, 2022 at 16:48
  • $\begingroup$ You may want to check at physics SE for similar questions, in particular whether there are asymmetrical magnetic fields on a universal scale, and why not. $\endgroup$
    – Buck Thorn
    Nov 1, 2022 at 18:52
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    $\begingroup$ One of the weird things of quantum mechanics is that most properties do not have defined values except when they are measured. Thus most electrons have neither +1/2 or -1/2 spin but rather exist in a superposition of both until we measure them. $\endgroup$
    – Andrew
    Nov 1, 2022 at 20:52


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