📚 Electronic Configurations | 电子构型
Electronic configuration describes how electrons are arranged in an atom. This arrangement controls chemical reactivity, bonding and physical properties. For Cambridge A-Level Chemistry, you must write configurations for elements up to krypton, interpret s, p, d notation, and explain exceptions such as chromium and copper.
电子构型描述电子在原子中的排布方式。这种排布决定了化学反应活性、化学键和物理性质。在剑桥 A-Level 化学中，你需要书写直至氪的元素电子构型，解释 s、p、d 符号，并说明铬和铜等特例。
1. Energy Levels and Sub-shells | 能级与亚层
h level is split into sub-shells labelled s, p, d and f. The first level has only 1s; the second has 2s and 2p; the third has 3s, 3p and 3d; the fourth has 4s, 4p, 4d and 4f.
电子占据主能级，编号为 n = 1、2、3 等。每个能级分为若干亚层，标记为 s、p、d 和 f。第一能级只有 1s；第二能级有 2s 和 2p；第三能级有 3s、3p 和 3d；第四能级有 4s、4p、4d 和 4f。
- n = 1: 1s only | n = 1：仅 1s
- n = 2: 2s, 2p | n = 2：2s、2p
- n = 3: 3s, 3p, 3d | n = 3：3s、3p、3d
- n = 4: 4s, 4p, 4d, 4f | n = 4：4s、4p、4d、4f
2. Orbitals and Their Shapes | 轨道及其形状
A sub-shell contains orbitals. An orbital is a region of space where there is a high probability of finding an electron. Each orbital can hold a maximum of two electrons. An s sub-shell has 1 orbital, p has 3, d has 5 and f has 7.
每个亚层包含若干轨道。轨道是空间中发现电子概率较高的区域。每个轨道最多容纳两个电子。s 亚层有 1 个轨道，p 有 3 个，d 有 5 个，f 有 7 个。
| Sub-shell | 亚层 | Number of orbitals | 轨道数 | Maximum electrons | 最大电子数 |
|---|---|---|
| s | 1 | 2 |
| p | 3 | 6 |
| d | 5 | 10 |
| f | 7 | 14 |
3. s, p, d and f Blocks | s、p、d、f 区
The periodic table can be divided into blocks based on the sub-shell being filled. Groups 1 and 2 form the s-block; groups 13 to 18 form the p-block; transition metals in groups 3 to 12 form the d-block; and the lanthanides and actinides form the f-block.
周期表可以根据正在填充的亚层划分为不同区。第 1 族和第 2 族构成 s 区；第 13 至 18 族构成 p 区；第 3 至 12 族的过渡金属构成 d 区；镧系和锕系元素构成 f 区。
- s-block: Groups 1 and 2, outermost electrons in s orbital | s 区：第 1、2 族，最外层电子在 s 轨道
- p-block: Groups 13 to 18, outermost electrons in p orbital | p 区：第 13 至 18 族，最外层电子在 p 轨道
- d-block: Transition metals, outermost electrons in d orbital | d 区：过渡金属，最外层电子在 d 轨道
- f-block: Lanthanides and actinides, outermost electrons in f orbital | f 区：镧系和锕系元素，最外层电子在 f 轨道
4. Aufbau Principle | 构造原理
hough n = 4 is larger than n = 3, because 4s is lower in energy than 3d for neutral atoms.
构造原理指出电子按照能量递增的顺序填充轨道。最初元素的顺序为：1s、2s、2p、3s、3p、4s、3d、4p。注意 4s 在 3d 之前填充，尽管 n = 4 大于 n = 3，因为对于中性原子，4s 的能量低于 3d。
1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p
5. Pauli Exclusion Principle | 泡利不相容原理
The Pauli exclusion principle states that no two electrons in an atom can have the same set of four quantum numbers. In practice, this means an orbital can hold at most two electrons, and those two must have opposite spins, represented by ↑ and ↓.
泡利不相容原理指出，原子中不能有两个电子具有完全相同的四个量子数。实际上，这意味着一个轨道最多容纳两个电子，且这两个电子必须自旋相反，用 ↑ 和 ↓ 表示。
For example, the 2p sub-shell has three orbitals, so it can hold up to six electrons, with two electrons of opposite
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