There's not actually chemical covalent bonds that are formed but it's a non-covalent interaction, usually dominated by hydrogen bonding.
所以配体和受体之间不生成共价键,这是一种非共价化合反应,它们通常以氢键相联
Likewise, the element that is a good electron acceptor in an electron transfer reaction is going to be the element that is going to hog the electrons in a covalent bond.
同样的,这个元素在一个电子转移反应中,是个很好的受赠者它将成为在共价电子,中吸引电子的元素。
Now, usually this is a non-covalent interaction.
这通常是一种非共价化合反应
He introduced the concept of electronegativity which was a measure, therefore, it is quantitative, of the atom's ability to attract electrons within a covalent bond and developed a scale of electronegativity.
他引入了电负性这一概念,一个反映着原子在成共价键时吸引电子的能力的数据标度,因此这是数量上的,在共价电子中,电子原子能吸引电子,并发展为一定规模的电负性。
Not only did we figure out a way to describe how we quantify it, but we've also quantified how we tell the difference between covalent and ionic, and percent ionic character.
我们不仅想出了一个办法来描述,我们如何定量它,而且我们也定义,我们如何分辨共价性和离子性,以及离子百分数。
This is pure covalency. This is polar covalency.
这是平均共价,它是极性共价。
This is the homonuclear bond energy for hydrogen in pure hydrogen. There we have perfect covalency.
这是氢的同原子的共价能,在纯氢中,我们有完美的共价键。
But the beauty in this calculation is it shows that this concept of electron sharing in an unequal manner is sound and it gets you into the right ballpark.
但在这个计算过程中,真正漂亮的是对电子,非平均共价的考虑很完全,从而指引我们向一个正确的方向思考。
Now, if I get over here, HF, I know that fluorine is hogging the electron, so it is not equal sharing. It is over here.
那我们再看到这里,氟化氢,我知道氟在拉电子,所以它就不是平均共价。
If I look at a homonuclear molecule such as molecular hydrogen, this is perfect sharing.
如果我用这个测量表测氢分子,完全平均共价的分子。
What is the extreme of unequal sharing?
什么是非平均共价的极端?
Because this is a dipole, he chose the pole part of dipole to give us polar covalency.
这就是偶极,鲍林选择了偶极中“极“这一部分来,组成极性共价这个词向我们诠释。
And so Pauling went further and said this is the purely covalent component.
然后鲍林更进一步,说这是一个完全的共价成分。
So you can see that polar covalency is a tendency towards ionic bonding.
所以你看得出极性共价就是,趋向离子键的。
They say homonuclear. So this is purely covalent.
而是用的同核,嗯,这是完全共价的。
And you have the bond energy in HF.
你得到氟化氢的共价能。
The electrons here are shared equally.
电子是被平均共价的。
So this is perfect sharing, unequal sharing.
从左边开始依次是平均共价。
We're going to talk about this kind of non-covalent interaction more when we talk about the immune system, because one example of ligand and receptors that's important in the immune system are antigens - foreign molecules, and antibodies - molecules that we produce.
当我们讲到免疫系统的时候,会更详细地谈到这种非共价化合反应,因为在免疫系统中,一个重要的配体受体结合反应,就是抗原,即外源分子,与抗体,这个人体自身产生的分子结合
Well, if it is a good electron donor in an electron transfer reaction, if the same element finds itself in a covalent bond, it is going to be a good electron donor, although it is not full transfer.
如果它是一个在电子反应中,的好捐赠者,如果相同电子发现他在共价电子里,它将成为一个好的捐赠者,虽然没有完全转换。
And then he said there is a second term here, a contribution to the unequal sharing.
然后他说还有第二个条件,就是非平均共价的贡献。
And this turns out to have a bond strength of 435 kilojoules per mole.
这证明有每摩尔435焦的,的共价能。
This is the ultimate in unequal sharing and this is ionic.
这是非平均共价,的最终形式离子键。
This is purely covalent because all it is is homonuclear bond energies.
是一个完全的共价成分,他的理由是他们都是同核共价。
And why did he call it polar covalency?
为什么要称它为极性共价呢?
Just to give you a sense of what that means, if the 264 figure is pure covalency and the 344 is partial ionic character, what fraction of the 608 is 344? 344, which is partial ionic character, 57% divided by 608 times 100 is 57%.
它只是给你一个这样的概念,264千焦每摩是完全共价成分的键能,而344是离子成分的,344除以608是多少,344,是不完全的离子特性,除以608乘以100得到。
And here the electrons are actually donated, so this becomes F minus.
非平均共价,到这里,电子被完全提供给F,这是氟负离子。
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