If we go to the oxygen atom, now we're talking about starting with 6 in terms of valence electrons again, but instead of 2, you can see we have 6 lone pair electrons around the oxygen minus 1/2 of 2, so we have minus 1 is our formal charge.

如果我们分析氧原子的话，现在我们讨论的还是,从六个价电子开始，但孤对电子不再是两个了，你会看到氧周围,有六个孤对电子，再减去二的一半，因此我们有一个负的形式电荷。

麻省理工公开课 - 化学原理课程节选