So carbon has four valence electrons, so if we talk about c 2, again we're going to start filling in our molecular orbitals, and now we're going to have eight electrons to fill into our molecular orbitals.

碳有4个价电子，所以如果我们考虑C2的话，同样，我们开始填分子轨道，现在我们有8个电子,要填入分子轨道。

麻省理工公开课 - 化学原理课程节选