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Because aluminum ions have charge of plus three and oxygen ions have charge of minus two.
因为铝离子为正三价,氧为负二价。
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where we could have dinner and it was free of charge, that kind of thing.
我们可以在那里吃晚餐，而且完全免费，诸如此类的。
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So we could think about comparing the potassium ion to a sodium ion. They have the same charge of plus one.
我们可以想象比较一下钾离子,与钠离子，它们都同样带有正一价的电荷。
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Make sure you have batteries that are in a good state of charge in your calculator.
确保你的计算器电池,处在一个良好的状态。
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ve something like, recent study shows of 30,000 Canadians have gone for other countries for health treatments, even though they got it free of charge in Canada, ve get to pay for it somewhere else, and they go.
有大约，You’,最近调查显示是3万加拿大人,去别的国家,寻求医疗，即使在加拿大有免费的，他们在别处得付费，and，they’,他们还是选择出去。
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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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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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He shot alpha particles which have a charge of plus two.
他入射的阿尔法粒子带有两个正电荷。
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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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So, let's say we have an atomic number of 3, 3 that means we have 3 electrons, so we better hope to get our neutral atom that we have a charge of plus 3in the nucleus.
这也是很合理的，因为Z就是原子序数，假设原子序数是，那就有3个电子，那我们就希望,性原子有个带3个正电荷的原子核。
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So, if we think about the second case here where we have c n minus, now we're talking about a molecule with a net charge of negative 1.
那么，如果我们考虑的是第二个例子,也就是氰离子，那么现在我们讨论的是一个净电荷量为负一的分子。
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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。
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It turns out, and we're going to get the idea of shielding, so it's not going to actually +18 feel that full plus 18, but it'll feel a whole lot more than it will just feel in terms of a hydrogen atom where we only have a nuclear charge of one.
结果是我们会有,屏蔽的想法,所以它不会是完整的，但是它会比原子核电荷量,吸引力要大很多,只有1的氢原子的。
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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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And there is this separation which is a balance of attractive forces because the chloride is net negative and the sodium is net positive, but both of them, regardless of net charge, have electrons.
这里有一个平衡,引力的平衡,由于氯离子带有负的净电荷,钠离子带有正的净电荷，但是它们两个，没有考虑净电荷，电子。
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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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Often a good thing to start with is to put the lowest ionization energy atom in the middle, and if you don't have charge separation then go with that structure, but if you do find you have a lot of separation, such as the case in negative 2, positive 2, and minus 1, then you want to say wait a second, this is really bad in terms of formal charge, let me go ahead and see what other options I have here.
通常一开始把电离能最低的原子,放在中心位置就很好了，如果你发现电荷没有分开,那么这个结构就没问题了，但是如果你发现有很多分开的电荷，比如这种情况，有负二，正二和负一，那么你会想要说等一下，从形式电荷来看这很不好，让我去看看其它可能的选择。
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What we need to do is get rid of the Coulomb tag that we have - that's how we measure our electron charges - charge, and so we use this epsilon nought quite often, this permativity constant of a vacuum to make that conversion.
怎么量度电子电荷,所以我们会经常用到,这个epsilon，nought记号,这是真空中的介电常数,我们还要指出,这个介电常数。
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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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Again we have the charge of the nucleus on plus 2, +2 but let's say this time the electron now is going to be very, very close to the nucleus.
对于我们的氦原子，我们有一次得到了原子核电荷量为,但是我们说这次电子。
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So even if we strip an atom of all of its electrons, we still have that same amount of positive charge in the nucleus.
所以即使把一个原子的所有电子都拿走,原子核还是带那么多的正电。
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So if we have total +2 and complete shielding -1 where that can actually negate a full positive charge, because remember our nucleus is plus 2, +1 one of the electrons is minus 1, so if it totally blocks it, all we would have left from the nucleus is an effective charge of plus 1.
抵消一个完全的正电荷,因为记住我们的原子核是,其中一个电子是,所以如果它完全挡住了它，我们从原子核中留下的，全部有效电荷就是，所以，在我们的第一个例子中,我们的第一种极端情况。
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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。
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But we could, for example, look at a case where we have several different structures that look pretty good, and the one we want to determine as being the lowest energy structure is the one in which the absolute values of the formal charges are going to be lower, so essentially that they have less charge separation.
但是我们可能，比如，遇到一种情况,有好几个候选的路易斯结构看起来都挺好的，这时候我们就需要,通过比较哪个形式电荷的绝对值更低,来决定哪个结构的能量更低，本质上这个结构中分开的电荷更少。
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So what we see is that structure a is the most stable because we have the least separation of charge in the case of structure a.
因此我们看到结构，A，应该是最稳定的,因为这种情况下,分开的电荷最少。
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