And so we have a positive charge in the nucleus which is given by the number of protons.

在原子核上,有很多质子聚集而形成的正电荷。

麻省理工公开课 - 固态化学导论课程节选

Now the last thing is that because the neutron has no net charge, we can change neutron number.

现在，最后一件事是,因为中子没有净电子，我们可以改变中子数。

麻省理工公开课 - 固态化学导论课程节选

So, if we want to figure out the formal charge on the carbon, we need to take the number of valence electrons, so that's 4. We need to subtract the lone pair, what number is that? It's 2.

如果我们想算出碳原子的形式电荷，我们需要将价电子的个数，也就是四，减去孤对电子的个数，它是多少？是二。

麻省理工公开课 - 化学原理课程节选