Home > Community > Do electrons only fill 'spin up' first? Or could it start filling 'down spins' first? [duplicate]
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Omozokpea Daniel

Do electrons only fill 'spin up' first? Or could it start filling 'down spins' first? [duplicate]

Charles Ward  Follow

No it does not matter whether you start with 'spin up' or 'spin down' electrons as long as you are consistent: If you start filling some orbitals with 'spin up' electrons you will have to keep doing this for all the orbitals you want to fill.

But: The convention is that you start with 'spin up' as this usually is taken to represent the $\frac{1}{2} \! \hbar$ eigenvalue of the $z$ component of the spin angular momentum operator and you should adapt to that in order to avoid confusion.

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John Yelton  Follow
@jkim Well, there are a few subtleties and I dont know how much you actually know about quantum mechanics. But if you only want to use the Aufbau principle and put some up/down arrows into boxes to describe the electron configuration of atoms and molecules then the choice between up and down should be random. But: The convention is that you start with spin up as this usually is taken to represent the $+ \frac{1}{2} \! \hbar$ eigenvalue of the $z$ component of the spin angular momentum operator and you should adapt to that in order to avoid confusion.More
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Ian Pearse  Follow
awesome. thank you! Is it then, fair to say that up/down of the first filling will be random?More
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