定义Definition
sp³ 杂化是一个 s 轨道与三个 p 轨道混合，形成四个能量相同的 sp³ 杂化轨道。四个杂化轨道指向正四面体的四个顶点，彼此夹角 109.5°。
sp³ hybridisation mixes one s orbital with three p orbitals to give four equivalent sp³ hybrid orbitals, pointing to the corners of a regular tetrahedron at 109.5° to each other.
甲烷与烷烃Methane and alkanes
基态碳原子 2s² 2p² 只有两个未成对电子，却在甲烷中形成四个等同的 C–H 键。杂化理论的解释是：2s 电子激发到 2p 后，一个 2s 和三个 2p 轨道杂化为四个 sp³ 轨道，各与一个 H 的 1s 轨道重叠形成 σ 键，所以 CH₄ 为正四面体，H–C–H 键角 109.5°。烷烃中所有碳原子都是 sp³ 杂化，金刚石中每个碳也是。
A ground-state carbon atom, 2s² 2p², has only two unpaired electrons, yet methane has four identical C–H bonds. Hybridisation explains this: after a 2s electron is promoted to 2p, the 2s and three 2p orbitals mix into four sp³ orbitals, each overlapping an H 1s orbital to form a σ bond, so CH₄ is tetrahedral with H–C–H angles of 109.5°. Every carbon in an alkane is sp³, as is every carbon in diamond.
含孤对电子的 sp³ 杂化sp³ atoms with lone pairs
NH₃ 中的 N 和 H₂O 中的 O 也可看作 sp³ 杂化，只是部分杂化轨道被孤对电子占据。孤对电子对成键电子的排斥更强，使键角减小：NH₃ 为三角锥形，键角约 107°；H₂O 为 V 形，键角约 104.5°。
The N in NH₃ and the O in H₂O can also be regarded as sp³ hybridised, with some hybrids holding lone pairs. Lone pairs repel bonding pairs more strongly, closing the angles: NH₃ is trigonal pyramidal at about 107°, and H₂O is bent at about 104.5°.
判断方法How to recognise it
中心原子周围有四个电子对区域（σ 键与孤对电子数之和为 4）时为 sp³ 杂化，如 CH₄、NH₄⁺、CCl₄、H₂O、醇中的 O 和胺中的 N。sp³ 轨道含 25% 的 s 成分。
A central atom with four regions of electron density (σ bonds plus lone pairs equal to 4) is sp³ hybridised, as in CH₄, NH₄⁺, CCl₄ and H₂O, and the O of alcohols and N of amines. An sp³ orbital has 25% s character.
年表Timeline
- 1874
范特霍夫与勒贝尔提出碳的四面体构型
van 't Hoff and Le Bel propose the tetrahedral carbon atom
- 1931
鲍林提出杂化轨道，用 sp³ 解释甲烷的正四面体结构
Pauling introduces hybrid orbitals, using sp³ to explain tetrahedral methane