Pauli Exclusion Principle

[104904344]

Can someone explain why there can't be no more than 2e- per orbital? Why do their spins must be paired?

[Kate_Santoso_4F]

In short, the Pauli Exclusion Principle states that in an atom or molecule, no two electrons can have the same four quantum numbers. Because an orbital can only contain a maximum of two electrons, the two electrons must have opposing spins. The two spin states of an electron can be represented as clockwise or counterclockwise rotation around an axis passing through the electron.

[904914909]

This answer above is a great explanation!

[Catly Do 2E]

Essentially the Pauli exclusion principle doesn't allow the electrons to have the same exact quantum numbers. So to occupy the same orbital, the spin has to be different.