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So we can think about now doing bonding, and now we have four equal orbitals with one electronic each.
我们现在可以考虑成键了，现在我们有4个等价的轨道，每个上面有1个电子。
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And what you find is when you have a bonding orbital, the energy decreases compared to the atomic orbitals.
你们发现当你有个成键轨道的时候，相比原子轨道能量要降低。
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And so this lower level is called a bonding orbital, and it is a bonding molecular orbital.
所以能级较低的轨道叫做成键轨道，这就是成键分子轨道。
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And because of the way those antibonding orbitals are stacked, the two electrons go one each into those antibonding.
因为这样,反键轨道被堆积了，这两个电子都填到各自的反键轨道。
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And the other thing to point out is that the energy that an anti-bonding orbital is raised by, is the same amount as a bonding orbital is lowered by.
另外一个要指出的事情是,反键轨道引起的能量升高，和成键轨道引起的能量降低是相同的。
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When we talk about p orbitals the phase of the orbital becomes important once we talk about bonding, which hopefully you were happy to hear at the beginning of class we will get to soon.
对于ｐ轨道,当我们讨论到成键时，轨道的相位就变得非常重要了,这个我们马上就要讲到了。
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Now, from your book as well, this is the pz's of the two atomic orbitals forming the bonding orbital.
现在，也是你们书上，这是两个pz轨道,组成的成键轨道。
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All right, so we can now see a little bit of what the power of molecular orbital theory is in predicting what kind of bonds we're going to see in molecules, or whether or not we'll see this bonding occur at all.
好了，我们已经可以看到一点,分子轨道理论在预测分子中,所成的键或者分子，能不能成键方面的能力了。
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And this one here, because it is at a higher energy is called antibonding molecular orbital.
这里的这个，因为处在一个较高的能级,被叫做反键分子轨道能级。
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So again, this is an anti-bonding orbital, and what you see is that there is now less electron density between the two nuclei than there was when you had non-bonding.
同样的，这是反键轨道，你们看到当你有反键轨道的时候,两个原子核中间的电子密度更小了。
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You might have thought before we started talking about molecular orbital theory that non-bonding was the opposite of bonding, it's not, anti-bonding is the opposite of bonding, and anti-bonding is not non-bonding.
你也许在我们讨论分子轨道之前,就想过非成键时成键的反面，它不是，反键才是成键的反面，反键不是非成键。
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So if we take a look at nitrogen here, what you'll notice is we have thre available for bonding, - and we already have our lone pair -- one of our orbitals is already filled up.
如果我们看一下氮原子，我们注意到我们可以成3个键，我们已经有一个孤对-,其中的一个轨道已经被填满了。
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And to do this we're going to introduce valence bond theory, and the idea of hybridization of orbitals.
在这之前我们要引入价电子成键理论，和杂化轨道的概念。
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Molecular orbital theory, even at this very basic level, allowed us to predict that no, we're not going to see a true bond here, a strong bond.
即使在最基础的层次，分子轨道理论预计，我们不会看到一个键，一个强的键，。
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So any time I draw these molecular orbitals, I do my best, and I'm not always perfect, yet trying to make this energy different exactly the same for the anti-bonding orbital being raised, versus the bonding orbital being lowered.
所以我在画这些分子轨道的时候，虽然不是很完美，但我总是尽量,让反键轨道引起的，能量升高和成键轨道。
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But when we think about where anti-bonding orbitals should be, it should be higher in energy.
但当我们讨论反键轨道的时候，它的能量应该更高。
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So the way that you describe a bond is you describe the orbitals that the bond comes from, and also the symmetry of the bond.
描述一个键的办法,是描述形成键的轨道，以及键的对称性。
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I want to finish this discussion by including the anti-bonding orbital, and this is a tip for you when you're drawing your molecular orbital diagrams, any time you draw a bonding orbital, there is also an anti-bonding orbital that exists.
我想要以包含反键轨道,来结束这个讨论，告诉你们一个,画分子轨道图的小技巧，任何时候你画一个成键轨道，都会存在一个反键轨道。
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So we'll start to look at molecules and we'll see if we take two atoms and we fill in our molecular orbital and it turns out that they have more anti-bonding orbitals than bonding, that's -- a diatomic molecule we'll never see.
我们要看开始看一看分子,并且我们会发现如果我们,取两个原子并且填入分子轨道,结果是它们的反键轨道,比成键轨道更多，这就是-一个我们不会看到的二元子分子。
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And the last bond that we have here is a carbon-carbon bond, and this is our last p orbitals that are coming together.
最后一个键是碳碳键，这是最后一个组合的p轨道。
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If we think about bringing in those last two carbons, what you can see is that for every carbon, two of its hybrid orbitals are being used to bond to other carbons.
如果我们考虑引入最后两个碳原子，你会看到的是对于每个碳原子，其中的两个杂化轨道,和另外的碳原子成键。
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We can also talk about anti-bonding orbitals where we have destructive interference.
我们也可以讨论,相消干涉的反键轨道。
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So we're going to finish talking about molecular orbital theory, we'll switch over to discussing bonding in larger molecules, even larger than diatomic, so we'll move on to talking about valence bond theory and hybridization.
我们要结束关于分子轨道理论的讨论，转向讨论大分子的成键，比二原子分子更大的分子，我们会继续讨论价电子成键理论,和杂化。
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When you are done you have three electron pairs in bonding orbitals.
当你完成的时候,成键轨道上共有三对电子。
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You have two electrons in antibonding to kind of offset the bonding.
你有两个电子,在远离成键轨道的反键轨道上。
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Remember, we didn't hybridize the 2 p y orbital, so that's what we have left over to form these pi bonds.
记住，我们并没有杂化2py轨道，这是我们剩下的那个行成了π键。
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And then the antibonding which we don't care about.
然后他们的反键轨道我们不去管了。
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So that's the idea of a bonding molecular orbital.
这就是成键分子轨道的概念。
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So it's along the bond axis and it's between a carbon s p 2 hybrid, and then the hydrogen is just a 1 s orbital that we're combining here.
所以它是沿着键轴方向的,而且这里是一个碳sp2杂化轨道，和一个氢的1s轨道的结合,在这里我们可以合并他们。
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And this will be called pi of 2py molecular orbital.
我们会称它为2py分子轨道上的π键。
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