There are some exceptions, which we'll get to later, but the only a big exception here is with hydrogen, which has a special stability that's associated with two electrons.

但也有一些例外我们将以后再讲，但这里只有一个较大的例外，氢，它的稳定性比较特殊，只需要两个电子。

麻省理工公开课 - 化学原理课程节选