✔ 最佳答案
The statement「the 4s subshell has a lower energy level than the 3d subshell」is NOT always correct.
From H (1s1) to Ar (1s2 2s2 2p6 3s2 3p6), the 3d subshell has a lower energy level than the 4s subshell. (In these atoms, none of 3d and 4s subshells are filled.)
For K (1s2 2s2 2p6 3s2 3p6 4s1) and atoms of greater atomic number, the 4s subshell has a lower energy level than the 3d subshell.
In P atom, the 3d subshell has a lower energy level than the 4s subshell. When P (1s2 2s2 2p6 3s2 3px1 3py1 3pz1) atom is excited, one of the 3s electrons will promote to 3d orbitals, and the electronic configuration becomes 1s2 2s2 2p6 3s1 3px1 3py1 3pz1 4s1. The five half-filled valence orbitals are hybridized to give five sp3d orbitals.
2007-03-20 23:51:10 補充：
Subshells 間的 energy levels 高低與能量相差多少，各原子都不同。以氫為例，energy levels :1s 4s。由於 Ar 或以前的原子 (ground state)，3d 與 4s 都不會填入電子，所以它們的 energy levels 高低，很少提及，避免混亂。但此舉卻引起另一些混亂。
2007-03-20 23:53:41 補充：
打錯字，最尾的紅色字應是 1s2 2s2 2p6 3s1 3px1 3py1 3pz1 3d1 (不是4s1)。
2007-03-20 23:55:47 補充：
以氫為例，energy levels :.......4s = 4p = 4d = 4s3s = 3p = 3d2s = 2p1s
2007-03-20 23:56:21 補充：
以氫為例，energy levels :.......4s = 4p = 4d = 4f3s = 3p = 3d2s = 2p1s
