Electron spin and chemical properties

2018-02-23 08:04:46

I just learned about spin in class and I recall my professor vaguely mentioning how the spin of an electron is what determines certain chemical properties. I have trouble seeing why. Suppose an electron had no spin (which I know can't happen since electrons are fermions) but if they did, can we determine if some elements were chemically inert?

See, e.g, https://en.wikipedia.org/wiki/Spin_chemistry:

"bonds can only be formed between two electrons of opposite spin...Sometimes when a bond is broken in a particular manner, for example, when struck by photons, each electron in the bond relocates to each respective molecule, and a radical-pair is formed. Furthermore, the spin of each electron previously involved in the bond is conserved,[1][2]... which means that the radical-pair now formed is a singlet (each electron has opposite spin, as in the origin bond). As such, the reverse reaction, i.e. the reforming of a bond, called recombination, readily occurs. The radical-

  • See, e.g, https://en.wikipedia.org/wiki/Spin_chemistry:

    "bonds can only be formed between two electrons of opposite spin...Sometimes when a bond is broken in a particular manner, for example, when struck by photons, each electron in the bond relocates to each respective molecule, and a radical-pair is formed. Furthermore, the spin of each electron previously involved in the bond is conserved,[1][2]... which means that the radical-pair now formed is a singlet (each electron has opposite spin, as in the origin bond). As such, the reverse reaction, i.e. the reforming of a bond, called recombination, readily occurs. The radical-pair mechanism explains how external magnetic fields can prevent radical-pair recombination with Zeeman interactions, the interaction between spin and an external magnetic field, and shows how a higher occurrence of the triplet state accelerates radical reactions because triplets can only proceed to products, and singlets are in equilibrium with the reactants as

    2018-02-23 08:27:10
  • If electrons had no spin and if they were, therefore, bosons instead of fermions, our entire universe would be much different. If the electron were a boson, chemistry would be completely different. For example, in a bosonic electron universe:

    ...the biggest atom by volume would be the Hydrogen atom and it would

    be the same size as the Hydrogen atom in our universe which is the

    Bohr radius, $r_B$. However, for all other atoms, the effective radius

    would be $r_B/Z$. where $Z$ is the atomic number = the number of

    protons in the nucleus. The reason for this is that when electrons are

    bosons it will be possible for all of the electrons of the atom to be

    in the 1S orbital of the atom. But in our universe, the Pauli

    exclusion principle only allows two electrons in each distinct orbital

    - one with spin up and one with spin down. So in the bosonic universe the only time any electron would be in any higher orbital would be

    when it is temporarily excited to a higher orbita

    2018-02-23 09:30:35