1. The problem statement, all variables and given/known data Here are the following Electron Configurations of Phospohorus 1. 1s2 2s2 2p6 3s1 3p4 2. 1s3 2s3 2p6 3s2 3p1 3. 1s2 2s2 2p6 3s2 3p2 3d1 4. 1s2 2s2 2p6 3s2 2d1 3p2 5. 1s2 1p6 2s2 2p5 6. 1s2 2s2 2p6 3s2 3p3 Questions: Which of these have non-existent orbitals? Which of these violate Pauli's Principle? Which of these are in the excited state? Which of these are it's ground state? . The attempt at a solution Just double checking... since I want to get the full marks remaining for this question (got it wrong before, and it's allocated me a new element) Non-Existent Orbitals 4 & 5, No such thing as 2d and 1p orbitals. 6 is its ground state 1 & 3 are excited states, (the 3s orbitals aren't totally filled?) That leaves, 2, violating Pauli's principle, which honestly, I have no idea about. Could someone confirm these for me and perhaps enlighten me more on these. Thanks!