-
"One of the jobs of the president, whether you are named Bush or Obama, is to go out there and reassure people and to show you are in charge and to send a signal to potential enemies out there that this will not be tolerated by any American leader, and they did not project that power effectively,".
VOA: standard.2010.01.06
-
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。
-
So, if we compare the sulfur to the oxygen, the oxygen it turns out is more electronegative and that is what holds the negative charge in this molecule.
因此，如果我们来比一下硫和氧，氧应该有更高的电负性,而在这个分子中它确实有负的电荷。
-
So, I've got this tiny volume with, in the case of gold 79 plus of charge, and I've got some electrons out here somewhere, and the vast majority of the atom is nothing.
我认为这个小体积里面，比如金的79个正电荷，电子在外面的某些地方，原子里面大部分是空心的。
-
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。
-
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。
-
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。
-
0 And it has a mass of 9.11 times 10 to the minus 31 kilograms The charge compensation comes out of the nucleus with the proton and it is positive 1.6 times 10 to the minus 19 coulombs.
它的质量是9。11乘以0,到负31千克,电荷补偿来自于,有质子的原子核,它是+1。6*10^库伦。
-
And shielding is a little bit of a misnomer because it's not actually that's the electron's blocking the charge from another electron, it's more like you're canceling out a positive attractive force with a negative repulsive force.
屏蔽有一点点用词不当,因为它事实上不是,电子阻挡了来自另一个电子的电荷,它更像你在用一个负排斥力，抵消一个正吸引力,但是屏蔽是考虑这个问题,的很好的方式。
-
He also figured out that the charge of the nucleus was a plus ze.
但我们实验没有放射性,然后我们就能回答那个问题了。
-
Out of that he concludes charge must be quantized.
出于此结论，他总结出电荷是量子化的。
-
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。
-
The two sources of charge cancel each other out.
两个电荷源互相抵消。
-
So, shielding happens when you have more than one electron in an atom, and the reason that it's happening is because you're actually canceling out some of that positive charge from the nucleus or that attractive force with a repulsive force between two electrons.
所以当你们在原子中有多于一个电子,屏蔽就会发生，它之所以会发生的原因是,你们实际上抵消了,一些来自原子核的正电荷,或者来自吸引力,在两个电子之间。
-
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。
-
The electron completely canceled out 1 it's equivalent of charge from the nucleus, such that we only saw in a z effective of 1.
电子完全抵消了来自原子核的等量电荷,这样我们仅仅看到有效的z为，在极端案例b中。
-
And out here we have the charge on the electron as simply equal to e.
而原子外层的电子,只是电量和e的电量相等。
-
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。
-
We said that that second electron was so far out of the picture, that it had absolutely no affect on what the charge was felt by that first electron.
我们说第二个电子远离这张图片,这样它就彻底的对,第一个电子感觉到的电荷没有影响了,所以。
应用推荐