https://mazziotti.uchicago.edu/qcdictionary/p_terms/pauli_exclusion_principle/index.html The Pauli Exclusion Principle states that two electrons cannot occupy the same quantum state simultaneously. This principle arises because electrons are fermions, or particles with half-integer spins. In contrast with bosons, which have integer spins and can condense into a single quantum state, fermions must obey antisymmetry that demands each quantum state to be singly occupied. As such, electrons may not share all four of their quantum numbers. Hugo en-us