When we have just a single bond in them molecule, you have all the free rotation you want, you can just spin it around, there's nothing keeping it in place.

当我们在分子力只有一个单键时，你可以随意旋转，你可以让它转起来，没有什么东西能固定住它。

麻省理工公开课 - 化学原理课程节选

You can see that we have two unpaired electrons in this molecule here one in the pi 2 p x star, and one in the pi 2 p y star orbital.

你们可以看到我们这个,分子力有两个未配对电子,一个在π2px星，一个在π2py星轨道。

麻省理工公开课 - 化学原理课程节选