- #1
Silviu
- 624
- 11
Hello! I am a bit confused about the Pauli exclusion principle. Let's say I have 3 electrons. Due to energy considerations the first 2 go to the ground state, and they can be only 2 electrons there, because the position wavefunction has only one option ##\psi_{100}## (and again due to energy configurations it chooses the symmetrical state) and the spin picks the anti-symmetrical so that it respect the fermions statistics overall. Hence, as there is no free state here, the 3rd electron goes to the next energy level ##\psi_{200}##. What confuses me is, how does the 3rd electron know the spins of the first 2? The 2 electrons in the ground state, don't need to have a precise value of the z component of the spin, it can be a linear combination of up and down. Of course, upon measurement, if one of them turns out to be up, the other one is necessary down, but for a random atom, before any measurement the up and down positions of the spin (in the z direction) are not occupied yet, as they are not measured, so how is the 3rd electron prevented to go there? I.e. the state (1,0,0,up) and (1,0,0,down) are not taken, as the 2 electrons are a linear combinations of them.