Define Pauli exclusion principle. Why is it called the exclusion principle?

According to the Pauli exclusion principle, no two electrons in a single atom will have the same set of quantum numbers (n, l, m, and s). To put it simply, each electron should have or be in its own distinct state (singlet state).

The Pauli Exclusion Principle follows two important rules:

• Only two electrons can share an orbital.
• The two electrons in the same orbital must have opposite spins or they are antiparallel.

According to the exclusion principle, if one electron in an atom has the same particular values for the four quantum numbers, then all other electrons in that atom are excluded from having the same set of values.

Final Answer: According to Pauli's Exclusion Principle, no two electrons in the same atom can have the same values for all four of their quantum numbers.