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So we'll talk specifically about drawing Lewis structures and then about formal charge and resonance, which are within Lewis structures.
因此我们会专门讲一讲,如何来画路易斯结构,然后再讨论形式电荷与共振论，它们也属于路易斯结构的范畴。
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So now that we have enough practice drawing Lewis structures let's talk about actually figuring out this formal charge.
那么现在我们已经做了足够多的画路易斯结构的练习,让我们来讨论一下如何得出形式电荷。
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So why don't you tell me what the formal charge should be on the sulfur atom of thionyl chloride?
那么请大家来告诉我亚硫酰氯中,的硫原子应该有多少形式电荷？
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actually our third, but the second one we're going to talk about in terms of formal charge, which is thionyl chloride.
实际上是第三个，但它是第二个,形式电荷的例子，也就是亚硫酰氯。
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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。
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So for example, that might have a formal charge of negative 1, because to some extent it has gained that much electron density that it now has a formal charge that's negative.
比如，可能它的形式电荷为负一，因为在一定程度上它得到了这么多的共用电子密度,那么它现在就有了负的形式电荷。
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And the last thing we do for any of our structures to check them and figure out are these valid or not valid, are these good Lewis structures is to check the formal charge.
而为了检验任何一个结构是否有效,看它们是不是好的路易斯结构,我们要做的最后一件事就是检查形式电荷。
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All right. So formal charge can actually help us out when we're trying to decide between several Lewis structures that look like they might be comparable in terms of which might be the lower energy or the more stable structure.
好的，形式电荷真的可以,帮助我们决定,在几种路易斯结构中,哪个更可能符合能量更低,或者结构更稳定的要求。
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So we can do this for any final charge we have, if we have a molecule that has a charge of plus 2, then all of the formal charges should add up to plus 2 and so on.
对于任意净电荷的情况,我们都可以这样做，比如假设我们有一个带两个正电荷的分子，那么所有的形式电荷加起来应该等于正二，等等。
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And it does, so we know that we're probably on target in terms of calculating our formal charge.
而它确实是这样，因此我们知道我们很有可能,算对了我们的形式电荷。
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So, in this case, we see that our formal charge is negative on the nitrogen, in this case it's negative on oxygen.
那么，在这种情况下，我们看到氮的形式电荷是负的，而在这种情况下，氧的是负的。
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And our eighth step in the process, again, is formal charge, which we will talk about very soon.
而我们流程中的第八步，同样是，形式电荷，我们很快就会讨论它。
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All right. So let's try one more example of drawing Lewis structures before we talk about formal charge.
好，让我们在讲形式电荷之前,再给一个例子画一下路易斯结构。
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And then we end up having 6 shared electrons, 2 from each of the bonds, so we end up with a formal charge on sulfur of plus 1.
然后我们有六个共用电子，每个键两个，因此最终硫的形式电荷量为正一。
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So when we talk about formal charge, basically formal charge is the measure of the extent to which an individual atom within your molecule has either gained or lost an electron.
说到形式电荷，基本上形式电荷就是,单个原子在形成分子之后,是得到了电子还是失去了电子的一种量度。
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The examples we've done so far have been pretty straightforward, so we haven't needed to use formal charge to make this kind of decision.
我们之前做过的例题,都是非常简单直接的，因此我们还不需要,用形式电荷来做这种决定。
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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。
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But I want you to tell me in terms of thinking about formal charge, which Lewis structure would you predict to be the most stable?
但我想让大家告诉我,从形式电荷的角度考虑，你会预测哪一个路易斯结构是最稳定的？
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So, these are the different ways that we can actually go ahead and use formal charge when we're choosing between different types of Lewis structures.
那么，这些就是在我们需要在,不同的路易斯结构之间做选择的时候,我们如何用形式电荷来进行判断的各种方法。
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So now we're done, actually there is one more step, which is to determine the formal charge.
那么我们现在做完了，实际上应该还有一步，那就是确定形式电荷。
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But what I'm going to tell you already is this is a case where, in fact, it's an exception to the idea that the lowest energy structure has the lowest ionization energy in the middle, and we can figure this out when we look at formal charge.
但是我已经告诉大家这个例子，实际上，是中心原子电离能最低的结构,的能量最低这一思路的一个例外，我们可以通过形式电荷看出这一点。
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We'll get to oxidation number in the second half of this course, but it's not in any way the same idea as formal charge.
我们会在课程的后半部分讲到氧化数，但它和形式电荷完全不是同一个概念。
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So hopefully next time we do a formal charge question, we'll get everyone back up to speed.
希望我们下一次做关于形式电荷的问题的时候，大家能够做得快一点。
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We haven't actually learned how to calculate the formal charge yet, we'll learn it soon.
实际上我们还没学如何计算形式电荷，我们很快就会学到了。
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So, we can also get into a case where we have similar values in terms of absolute values of formal charge between two different molecules we're deciding between in their Lewis structures.
我们还可能遇到另外一种情况,那就是在我们需要进行,选择的两种路易斯结构中,形式电荷具有相似的绝对值。
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So that means if we add up all of the formal charges within the molecule, what we would expect to see is that they sum up to give a net charge of negative 1.
那么这就意味着如果我们把这个分子中,所有的形式电荷加起来，我们应该会看到它们加起来,之后得到的净电荷量为负一。
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So in our first structure, we would find for the nitrogen we have a formal charge 5 minus 4 minus 2, because we're starting with 5 valence electrons, so that is a formal charge of minus 1.
那么在我们的第一个结构中，我们发现氮的形式电荷量是五减去四4,再减去二，因为我们开始有五个价电子，因此它的形式电荷量是负一。
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So what we see is that the formal charge on the nitrogen is 0.
因此我们看到氮的形式电荷是零。
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And what's important to keep in mind about formal charge is if we have a neutral atom, such as we did in thionyl chloride here, the sum of the individual formal charges on individual atoms within the molecule have to equal 0.
而关于形式电荷记住一点是很重要的,那就是如果我们有一个中性原子，比如亚硫酰氯，那么这个分子中的所有原子的,形式电荷之和应该等于零。
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