The configuration 1s² 2s⁰ 2p⁰ 3s¹ violates which principle?

1. The Aufbau principle says electrons fill the lowest available energy level first. 2. Here 2s and 2p are both empty while 3s, which lies higher in energy, holds an electron. 3. That electron should have entered 2s first, so the building-up order is broken. 4. Hund's rule governs how electrons spread within one subshell, which is not the issue here. 5. The Pauli principle forbids more than two electrons per orbital, and no orbital here is overfilled. _Source: NECTA ACSEE 2023 Chemistry 132/1, Question 4: The Atom_