For the carbon, we start with 4 valence electrons, we have 0 lone pair electrons minus 4, and we end up with a formal charge of 0.

对于碳，我们从四个价电子开始，我们有零个孤对电子，再减去四，最终我们有零个形式电荷。

麻省理工公开课 - 化学原理课程节选

If these bonds were all completely of equal distance apart, whether is was a lone pair or bonding electrons, 5° the angles would be 109 . 5 degrees.

如果不管它是孤对，还是成键，它们等距分开的话，键角是109。

麻省理工公开课 - 化学原理课程节选

Yeah, so also 4. We started with 10 valence electrons, we used up 6 of those as bonding electrons, so we have 4 left, which will be lone pair electrons.

对，也是四个，我们从十个价电子开始，只用了六个来成键，因此我们还剩下四个，它们将成为孤对电子。

麻省理工公开课 - 化学原理课程节选

So in oxygen we have a similar situation where, in fact, we are not going to promote any of the electrons because we have two lone pair electrons no matter what we do.

在氧中，情况很类似，我们不能激发电子,因为无论如何我们都有两个孤对电子。

麻省理工公开课 - 化学原理课程节选

So in terms of nitrogen that starts off with a valence number of 5, again we have 2 lone pair electrons in the nitrogen, and again, we have 6 electrons that are shared.

对于氮来说,我们应该从五个价电子开始，同样，氮也有两个孤对电子，共用电子的个数也一样，是六个。

麻省理工公开课 - 化学原理课程节选

For the sulfur, we start off with 6 valence electrons, minus 4 lone pair electrons, minus 2, taking in account our bonding electrons, so we end up with a formal charge of 0.

对于硫，我们从六个价电子开始，减去四个孤对电子，再减去二，算上我们的成键电子，因此最终我们有零个形式电荷。

麻省理工公开课 - 化学原理课程节选

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

And if we talk about chlorine, and both of the chlorines are the same in this case, we start with a valence number of 7 for chlorine, and then we subtract 6, because it had 6 lone pair electrons around each of the chlorine atoms.

而如果我们讨论氯的话，在这个例子中两个氯的情况都是一样的，从七个价电子开始，然后减去六，因为每个氯原子周围,都有六个孤对电子。

麻省理工公开课 - 化学原理课程节选

So what we see is on ammonia here, 107 we know that it's less than a 109 . 5, it's actually 107, so it's less than a 109 . 5, because of that lone pair pushing down in the bonding electrons.

我们看到在氨分子里，我们知道它比１０９．５要小，它是，所以比109。5要小，因为孤对会把成键电子向下推。

麻省理工公开课 - 化学原理课程节选

So, which atom is in need of those lone pair electrons?

那么，哪个原子需要这对孤对电子呢？

麻省理工公开课 - 化学原理课程节选

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