碳的化合价是四价。
And by now, I mean the valence electrons.
迄今为止，我指的是价电子。
How many valence electrons do we have left?
我们还剩下多少个价电子？
It's got a very low average valence electron energy.
它的平均价电子能很低。
Because it is not the valence shell. Forget about it.
因为它不是价层电子，所以忘记它吧。
So let's think about methane using valence bond theory.
让我们用价电子成键理论来看一看甲烷。
A closely related concept is that of free valence.
一个密切有关的概念是自由价。
We actually need to think about those valence electrons.
我们需要考虑这些价电子。
For our step two, what we need is number of valence electrons.
我们的第二步，需要知道价电子的个数。
How many do we need to get full valence shells everywhere?
要得到全部是满壳层需要多少个？
All right, well, oxygen has the highest valence electron energy.
好吧，氧具有最高价电子平均能。
So the idea behind valence bond theory is very easy to understand.
价电子成键理论，非常容易理解。
The bent bond states mainly appear near the top of valence band.
弯键态主要出现在价带顶附近。
So let's think about what the valence electron configuration is here.
让我们看看这里的，电子构型是什么样的。
The influence of two valence metal on gel strength of AGAR is remarkable.
二价金属元素的存在对琼脂的凝胶强度影响最为显著。
The same valence emotion impact on the attention is completely different.
同一种效价的积极情绪对注意范围的影响是完全不同的。
Now here is fluorine, same skeleton, only fluorine has seven valence electrons.
这是氟，同样的结构，只有氟有七个价电子。
So, hopefully, you remember what we mean by valence electrons versus core electrons.
希望大家还记得，价电子与芯电子的定义。
And I want to point out the difference between core electrons and valence electrons here.
我想指出的是，核电子和价电子，之间的区别。
PROFESSOR: five — there's five valence electrons, but the atomic number is actually seven.
教授：5，有5个价电子，但原子序数是7。
For example, we can talk about nitrogen, and nitrogen has five valence electrons shown here.
例如，我们可以讨论氮原子，氮原子有5个价电子。
The experimental result, show an increase of both conduction and valence band tail states.
实验结果表明：光照以后，导带尾态和价带尾态都增加了。
The experimental result, show an increase of both conduction and valence band tail states.
实验结果表明：光照以后，导带尾态和价带尾态都增加了。
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