Science (9th Grade)
Electron Subshells
Which of the following represents the correct filling order of the electron subshells?
1s, 2s, 2p, 3s, 3p, 4s, 3d
1s, 2s, 2p, 3s, 4s, 3p, 3d
1s, 2p, 2s, 3s, 3p, 4s, 3d
1s, 2s, 3s, 2p, 3p, 4s, 3d