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times 7, plus we have 6 in the sulfur, and oxygen is right above sulfur, so that also has 6.
二乘上七，加上硫的六个，而氧在硫的正上方，因此也有六个。
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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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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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To actually apply this it helps to go to something called the normal approximation to the binomial, because it's kind of difficult to compute this formula.
在实际应用这些公式的时候,需要运用二项分布的正态近似定理,因为二项分布公式的值很难计算
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And what you find out if you do these calculations, is that you have a negative 1 for your formal charge on nitrogen, you have a negative 2 for your formal charge on carbon, and you have a positive 2 for your formal charge on sulfur.
而如果你做了这些计算会发现，氮的形式电荷量为负一，碳的形式电荷量为负二，而硫的形式电荷量为正二。
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I didn't use the normal approximation there-- that's obvious--I used the binomial itself.
我显然并没有用到正态分布,我用了二项分布
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If we look at our last structure here where we have nitrogen the middle, we can also figure out all those formal charges, and in this case we have plus 1 on the nitrogen, we have minus 2 on the carbon, and then we end up with a 0 on the sulfur there.
如果我们来看看最后一个结构,在中间的原子是氮，我们同样可以计算出所有的形式电荷，而在这种情况下，氮为正一，碳为负二，而最后硫为零。
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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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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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So, what we call this is the third ionization energy, or the negative of the binding energy, again of the 2 s orbital, but now it's in boron plus 2 to we're starting with.
那么我们称它为第三电离能，或者负的束缚能，还是，2，s，轨道的，但现在我们是从正二价硼离子开始的。
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The highest occupied orbital is now the 2 s orbital, 1 s 2 2 s 1 so we're going to end up with boron 2 plus 1 s 2, 2 s 1, plus the electron coming out of there.
现在最高的被占据轨道是，2，s，轨道，因此结果应该是正二价的硼，再加上一个出射的电子。
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