sp²杂化sp2 hybridization

乙烯中每个碳原子 sp² 杂化：三个杂化轨道分别与两个 H 和另一个 C 形成 σ 键，两个碳上未杂化的 p 轨道侧面重叠形成 π 键，所以乙烯六个原子共平面、键角约 120°。BF₃ 中硼原子 sp² 杂化，分子为平面三角形。醛、酮的羰基碳、羧酸根中的碳、苯环和石墨中的碳都是 sp² 杂化。

Each carbon in ethene is sp² hybridised: its three hybrids form σ bonds to two H and the other C, and the unhybridised p orbitals on the two carbons overlap sideways to form the π bond, so all six atoms are coplanar with angles of about 120°. Boron in BF₃ is sp² hybridised, giving a trigonal planar molecule. The carbonyl carbon of aldehydes and ketones, the carbon in carboxylate ions, and the carbons of benzene and graphite are all sp².

中心原子周围有三个电子对区域（σ 键和孤对电子的总数为 3）时，通常为 sp² 杂化。对碳原子而言，含一个双键、两个单键的碳是 sp²；只含单键的碳是 sp³；含三键或两个双键的碳是 sp。

A central atom with three regions of electron density (σ bonds plus lone pairs equal to 3) is usually sp² hybridised. For carbon, a carbon with one double bond and two single bonds is sp²; one with only single bonds is sp³; one with a triple bond or two double bonds is sp.

sp² 碳的平面结构使相邻的 p 轨道可以平行重叠，形成离域 π 体系，这是苯稳定、石墨导电的原因。sp² 轨道中 s 成分占三分之一，多于 sp³ 的四分之一，所以 sp² 碳的 C–H 键略短、略强。

The planar geometry of sp² carbons lets neighbouring p orbitals overlap in parallel to form delocalised π systems, which is why benzene is stable and graphite conducts. An sp² orbital is one-third s character, more than the one-quarter of sp³, so C–H bonds to sp² carbon are slightly shorter and stronger.