定义Definition
电子排布是原子或离子中的电子在各电子层、亚层和轨道上的分布方式，常用 1s² 2s² 2p⁶ 这样的式子表示：数字为电子层，字母为亚层，上标为该亚层的电子数。基态电子排布按能量最低原理、泡利不相容原理和洪特规则确定。
The electron configuration is how the electrons of an atom or ion are distributed among shells, subshells and orbitals, usually written in the form 1s² 2s² 2p⁶: the number is the shell, the letter the subshell and the superscript the number of electrons in it. The ground-state configuration follows the aufbau principle, the Pauli exclusion principle and Hund's rule.
书写方法How to write it
按亚层能量从低到高的顺序填入电子：1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p……例如 Na 为 1s² 2s² 2p⁶ 3s¹，Fe 为 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²。可以用稀有气体符号代替内层电子，简写为 [Ne] 3s¹、[Ar] 3d⁶ 4s²。用方框和箭头表示每个轨道中电子的排布图，能显示未成对电子的数目。
Fill subshells in order of increasing energy: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p… For example Na is 1s² 2s² 2p⁶ 3s¹ and Fe is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s². The inner electrons can be replaced by a noble-gas symbol: [Ne] 3s¹, [Ar] 3d⁶ 4s². Orbital box diagrams, with arrows for electrons in each orbital, show how many electrons are unpaired.
特例与离子Exceptions and ions
铬和铜是常见特例：Cr 为 [Ar] 3d⁵ 4s¹，Cu 为 [Ar] 3d¹⁰ 4s¹，半充满或全充满的 3d 亚层使能量更低。过渡金属形成阳离子时先失去 4s 电子，再失去 3d 电子：Fe²⁺ 为 [Ar] 3d⁶，Fe³⁺ 为 [Ar] 3d⁵。阴离子则在原有排布上加电子，如 Cl⁻ 为 [Ne] 3s² 3p⁶。
Chromium and copper are common exceptions: Cr is [Ar] 3d⁵ 4s¹ and Cu is [Ar] 3d¹⁰ 4s¹, because a half-filled or filled 3d subshell lowers the energy. Transition metals lose their 4s electrons before 3d when forming cations: Fe²⁺ is [Ar] 3d⁶ and Fe³⁺ is [Ar] 3d⁵. Anions add electrons to the atom's configuration, e.g. Cl⁻ is [Ne] 3s² 3p⁶.
与周期表的关系Link to the periodic table
周期表的结构反映了电子排布：周期数等于最外电子层的序数，主族元素的族序数与最外层电子数相关。最后填入电子的亚层决定元素所在的区：s 区（第 1、2 族）、p 区（第 13–18 族）、d 区（过渡元素）和 f 区（镧系、锕系）。同族元素最外层电子排布相似，所以化学性质相似。
The layout of the periodic table reflects electron configuration: the period number is the number of the outer shell, and the group of a main-group element relates to its outer electrons. The subshell being filled last fixes the block: s block (groups 1 and 2), p block (groups 13–18), d block (transition elements) and f block (lanthanides and actinides). Elements in a group have similar outer configurations and so similar chemistry.
年表Timeline
- 1913
玻尔提出电子在一定能级上运动的原子模型
Bohr proposes the atomic model with electrons in fixed energy levels
- 1922
玻尔用电子层的逐步填充解释周期表
Bohr explains the periodic table by the successive filling of shells
- 1924
斯托纳提出按亚层分配电子的方案
Stoner proposes distributing electrons among subshells
- 1925
泡利提出不相容原理
Pauli states the exclusion principle
- 1936
马德隆总结 n + l 填充顺序规则
Madelung formulates the n + l ordering rule