So essentially, we have two ethene or ethylene molecules here to start with where these blue are our 2 s p 2 hybrid orbitals, so you can see that for each carbon atom, one is already used up binding to another carbon atom.

本质上，我们从两个乙烯分子开始,蓝色的是2sp2杂化轨道，你可以看到，对于每一个碳原子，其中一个已经用来和另外一个碳原子成键。

麻省理工公开课 - 化学原理课程节选