Pauli exclusionj priniciple states that two electrons cannot have the same quantum state.
These are valid representations:
⇅ ⇅ ↑
⇅ ⇅ ↑ ↑ ↑
⇅ ↑
This is not valid:
⇵ ↑↑ because it shows that the two last electrons occupy the same orbital with the same spin number, which means that those two electrons have the same identical quantum numbers, in violation of Pauli exclusion principle.
