Multiple choice Which of the following configurations is not possible? 1s2 2s2 2p7 1s2 2s2 sp6 1s2 2s2 2p5 1s2 2s2 Reveal answer Fill a bubble to check yourself A Correct answer Explanation The p-subshell can hold maximum 6 electrons (Pauli exclusion principle: 3 orbitals × 2 electrons). Option A shows 2p^7 which is impossible. Option B has a typo but 2p^6 is valid.