Why each energy state is having only 1 electron?

1. Feb 28, 2015

Why each energy state is having only 1 Fermion or electron instead of 2?
as we know fermions or electrons obey pauli's exclusion principal so 1 state can have two electrons with different spin (i.e if one spins up then second spins down) isn't it???

2. Feb 28, 2015

jfizzix

Each orbital can hold two electrons because they have two different spin states. The complete state of both electrons is not identical, so Pauli's exclusion principle doesn't prevent two electrons with different spin states from occupying the same orbital.

3. Feb 28, 2015

Ya...I know 2 electron can occupy 1 energy state. But in Fermi-Dirac statistics there is mentioned that "only one electron can occupy one energy state"....!!!

4. Feb 28, 2015

jfizzix

Fermi-Dirac statistics say that only one electron can occupy one quantum state.

The complete quantum state of an electron would include both its energy state and its spin state, so there's no conflict.

5. Feb 28, 2015

jfizzix

Note that there is a factor of two in describing Fermi-Dirac statistics in the context of thermodynamics and such.