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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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And these, by the way, are called Lewis structures.
就这些，顺便说下，这些都是Lewis结构式。
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So he came up with the ideas that led to the idea of Lewis structures in the very early 1900's.
他就提出了这个想法,进而发展出了路易斯结构在二十世纪初。
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So in terms of remaining valence electrons we have 12, so we can finish off each of our Lewis structures, so that's our first structure there, and our second structure there.
那么关于剩下的价电子，我们有十二个，因此我们可以完成这两个路易斯结构了，那么这是我们的第一个结构，而那是我们的第二个结构。
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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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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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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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And I mean this means way past all the chemistry they've taken, they're now graduate students or they're now professors, and they're still writing out Lewis structures.
我想说的是这意味着尽管他们早就学完了所有的化学，他们现在都已经是研究生甚至是教授了，但他们依然在不断地写路易斯结构。
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So, to do this, what I'm going to do is introduce the topic of Lewis structures.
那么，了做到这一点，我将开始介绍,路易斯结构。
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We're going to really get into this next class, but I just want to introduce it to you to give us a start, and many of you have used Lewis structures in high school, but we'll be doing some much more challenging Lewis structures, I can assure you, in this class here.
其实我们下节课才会详细介绍它，但是今天我只想以简单介绍作为开始，大部分同学在高中就用过路易斯结构了，但是我们会遇到一些更具挑战性的,路易斯结构，我可以向大家保证，在这门课中会的。
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A lot of the examples that we're going to give you in terms of trying out your Lewis structures will be molecule that are used in organic synthesis, or maybe they're molecules that react in interesting ways with biomolecules in your body or proteins in your body.
很多我们将要用来,训练路易斯结构的例子,都是在有机合成中用到的分子，也有可能是那些在你体内的生物分子,或者蛋白质中发生有趣反应的分子。
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So, Lewis structures are really a model for a way to think about what the valence electron configuration is, and as I said, it's not based on quantum mechanics, it's something that Lewis observed far, far before quantum mechanics were discovered.
路易斯结构实际上是一个用来考虑价,电子排布的模型，而就像我说的，它并不以量子力学为基础，而是路易斯在以前发现的,在量子力学出现很早前。
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And resonance is the idea that sometimes one single Lewis structure does not adequately describe the electron configuration around a given molecule, so instead you need to draw two different Lewis structures to describe that more appropriately.
而所谓共振态,就是有时候一个路易斯结构不足以,完整描述一个给定分子的电子排布，因此这时你需要同时画出两个,不同的路易斯结构来描述它,这样会更恰当。
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- So what we're seeing is this is notes from 1902 -- he actually didn't publish any of this work or these ideas that led to Lewis structures until 1916, but his early class notes were used as evidence about how long ago he actually came up with the idea of it.
我们看到的这是，1902，年的讲义-,实际上他直到1916年才发表这些工作或者想法,后来发展成为了路易斯结构，但他早年上课的讲义却成为了他在多久之前,就产生了这个想法的证据。
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So remember, that when we talked about Lewis structure, the organizing principle behind Lewis structures is the idea that within the molecule the atoms are going to arrange their valence electrons, such that each atom within the molecule has a complete octet or full outer shell.
记得，当我们讨论路易斯结构的时候，路易斯结构所遵循的组织原则是这样一种思路,那就是分子中的原子都倾向于,重新安排它们的价电子,使得分子有一个完整的,“八隅体“或者排满的外壳层。
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But since in drawing Lewis structures actually, in some cases you do, you can draw a dotted line that means a 1 and 1/2 bond, but most in most cases, we just draw out both resonance structures, and the way that we say it's a resonance structure is that we put it in the brackets and we put an arrow between it.
但是由于在画路易斯结构时,其实，在某些情况下是可以的，你可以画一条虚线来表示一又二分之一键，但是在多数情况下，我们就把两个结构都画出来，而我们说这是一个共振结构的表示的方法是,把它们放在括号里，并在中间放一个双箭头。
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It's always a good first approximation, because you need to start somewhere in terms of drawing Lewis structures, but then if you go and figure out the formal charge and you just have lots of charge separation or very high charges, like a plus 2 and a minus 2 and a minus 1 all different places in the atom, what it should tell you is maybe there's a better structure.
它总是一个好的第一近似，因为在画路易斯结构的时候,你总需要一个起点，但是如果你在算出形式电荷之后,发现有很多电荷分开了,或者说有很高的电荷，比如有一个正二，一个负二，还有一个负一1,在原子的各个地方，这应该就是在告诉你,或许还有一个更好的路易斯结构。
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And also I wanted to mention in terms of checking your Lewis structures, regardless of what they are, you should always go back and I had 10, and then count 2, 4, 6, 8, 10, because you always need to make sure you have the same number of valence electrons that you calculated in your actual structure.
我还想提一点关于检查,你的路易斯结构的建议，不管它们是什么，你总是应该回去检查一下,我有十个，然后数一数，二，四，六，八，十个，因为你总是需要确保实际价电子的数量,与你在结构中算出的数量相等。
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We don't always want to go and solve the Schrodinger equation, and in fact, once we start talking about molecules, I can imagine none of you, as much as you love math or physics, want to be trying to solve this Schrodinger equation in that case either. So, what Lewis structures allow us to do is over 90% of the time be correct in terms of figuring out what the electron configuration is.
我们并不想每次都去解薛定谔方程，而且实际上，一旦我们开始讨论分子，我可以想象,你们中没有一个人，不管你有多么热爱数学或物理，会想去解这种情况下的薛定谔方程,总之，路易斯结构能让我们,有超过，90%，的概率判断出正确的,电子排布。
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Once you're doing this on your own, -- especially, for example, on exam 2, which is a ways down the road, you won't be able to look at those steps, so you need to make sure that you can go through them without looking at them, but for now we can look at them as we are actually learning how to draw the Lewis structures, and rather just go through them step-by-step, it's more interesting to do it with an example.
每当你要画一个路易斯结构的时候，特别是，比如，在第二次考试中，在不远的将来，你将看不到这张表，因此你需要确保自己在不看这张表,的情况下也能按照上面的流程来画，但是目前我们是可以看着这张表,来学习如何画路易斯结构的，而相比于一步一步地讲，通过例子来演示一下会更有意思。
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But they're not accurate all the time in predicting bonding within molecules, and the reason for this is because Lewis structures are not, in fact, based on quantum mechanics.
但它们在预测分子内,成键时不总是正确的，这是因为Lewis结构，实际上不是基于量子力学的。
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And you can do this any time if you have Lewis structures that you're choosing between.
而每当你遇到需要从几个可能的,路易斯结构中选择的情况。
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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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We remember that Lewis structures are an idea that are pre-quantum mechanics.
我们记得路易斯结构是一个,早于量子力学的概念。
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So, today we're moving on, we're talking about Lewis structures.
那么，今天我们接着讲，继续讨论路易斯结构。
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All right, so one thing that I first want to point outabout MO theory that is a big difference from Lewis structures, is that in MO theory valence electrons are de-localized over the entire molecule.
好了，对于MO理论低一点要指出的,是它和Lewis有着很大的区别，在MO理论里,价电子在整个分子里是去局域化的。
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So, when we talked about Lewis structures, we actually assigned electrons to individual atoms or to individual bonds.
当我们讨论Lewis结构时，我们把每个电子指派到,各个原子或键上去。
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