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So if we go ahead and name this bond, what we're going to name it is sigma, - because that's the -- basically the shape of the bond or that's how our bond is coming together.
所以如果我们继续并且命名这一键，就是我们要命名的这个键，因为这是-,基本上键的形状,或者这就是键是怎么到一起的。
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So, as they're very quietly handing out your class notes, let's think about what this bond is here, this boxed bond, is it a pi bond or a sigma bond?
在他们发讲义的同时，我们来看看这个键，方框里的这个键，它是sigma键还是π键？
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I mean, hypothetically a bond trading at $.60 on the dollar with an 8% coupon, five-year bond that's yielding about 18%.
我的意思是，假设一种债券以0。60美元进行交易,同时有8%的票息，五年期债券收益率在18%左右。
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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。
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And again, this is between the p orbitals, these are not hybrid orbitals, so when we name this bond we're going to name it as a pi bond here, because it's between two p orbitals, and it's going to be between the carbon 2 p y orbital, and the other carbon 2 p y orbital.
同样，这是在p轨道之间的，它们不是杂化轨道，所以当我们命名这个键时,我们要命名它为π键，因为它在两个p轨道之间，而且是在碳2py轨道，和另一个碳2py轨道之间。
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So if we look at its length, it's actually shorter than a single bond, but longer than a double bond.
因此如果我们看它的键长的话，它实际上比单键更短，却比双键更长。
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So, if it's a four-year bond, it would trade at about $90, 6% so it would be yielding 6%.
所以，如果这是四年期的债券，那么它可能在大约90美元左右进行交易，因此它的收益率大约在。
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It's much more relevant to set our zero point energy as the separation of a bond in terms of talking about the reactions that we'll usually be dealing with here.
更好的是把零点能定在,键断裂的时刻,在讨论化学反应的时候,而我们以后将经常遇到化学反应。
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If it's symmetric, that means that each bond has exactly the same energy.
这意味着如果他们对称，那么每根键的能量是一样的。
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Now I want to ask, what's the nature of the carbon-hydrogen bond?
现在我想问问，碳氢键的本质是什么？
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So let's figure out the bond order for our two molecules here that we figured out the electron configuration for.
让我们看看这里,两个分子的键序是多少。
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It's going to be a stronger bond because it's more stabilized when it when it comes together as a molecule.
这将是一个更强的键，因为它会变得更加稳定,在形成分子之后。
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It's the most simple-- or often called a bill-- a discount bond does not pay interest; it's sold at a discount.
它是最简单的,经常被称为国库券,它是一种贴现债券,且不付息,并以折扣价发行
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So there's not a lot of room in the government bond market or other high-quality bond markets to generate excess returns.
所以对于政府债券或者优质债券,超额收益的空间不大
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The other thing that's happened now is that Warren Buffett said he wants to get into the municipal bond insuring business.
还有一件事,沃伦·巴菲特说,他希望介入市政债券保险这一领域
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So even though we see a nodal plane down the center, I just want to really point out that it's only when we have a nodal plane in the internuclear or the bond axis that we're calling that a pi orbital.
虽然在中间有个节面，我想要指出的是,只有节面在核间轴,或者键轴上时,我们才叫它π轨道。
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All right, so that's really all there is to thinking about valence bond theory in terms of the most simple explanation here.
好了，这就是,价电子轨道理论的,最简单的解释。
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Or if we look at how strong it is, it's actually stronger than a single bond, but weaker than a double bond.
或者如果我们看键的强度的话，它实际上比单键更强，而比双键更弱。
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All right, so let's think of a more complicated example of having a double bond, and maybe a more interesting example, and this is talking about benzene.
好了，让我们来看关于双键的,一个更复杂的例子，也许是更有趣的例子，我们要讨论苯环。
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And by that what we mean is that they're absolutely identical, and it turns out that this here is not a double bond, it's not a single bond either, it's actually something in between.
这意味着它们是绝对完全相同的，实际情况应该是这不是一个双键，这也不是一个单键，而是介于两者之间的状态。
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What we're going to do in forming a molecule is just bring these two orbitals close together such that now we have their nucleus, the two nuclei, at a distance apart that's equal to the bond length.
我们在形成一个分子时要做的就是,把这两个轨道放到一起,这样我们有他们的原子核，两个原子核，它们之间的距离为键长。
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It's a 1 and 1/2 because it's halfway between a double bond and a single bond.
是因为它介于,单键和双键中间。
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So it's very important that the double bond locks it in a particular conformation.
所以双键把它们锁定在某一特定形状,是十分重要的。
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If we think about that, that's a sigma bond, right, they're coming together along the nuclear axis.
如果我们考虑它的话，它是sigma键，对吧，它们沿着核轴方向靠近。
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So that is the bond axis it's just the axis between the two nuclei.
这就是键轴,它就是两个原子核之间的轴。
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Well, in '26, the-- i've shorted the one-period bond and so I have to pay out one dollar, but that's exactly what I wanted to do.
6年 我卖空的一年期债券到期了,我需要偿还一美元,不过这恰是我要做的
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So, when we think about a bond length, this is going to be the length of our bond here, that makes sense because it's going to want to be at that distance that minimizes the energy.
因此，当我们考虑一个键的长度的时候，这就应该是我们的键长，这是合理的,因为体系会在核间距达到这一距离时,能量到达最小值。
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So, for example, down here I wrote that it was n 2 and that it was h 2, but when I re-wrote the molecules up here, you saw that it's an h h single bond where it's a nitrogen-nitrogen triple bond.
比如，在这下面我写的是氮分子2,而这个是氢分子，但我在上面把这些分子的形式改写了，大家可以看到,这是一个氢与氢之间的单键，含一个氮与氮之间的三键。
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And we know that it's electron density between the nuclei that holds two atoms together in a bond.
我们知道是两个原子核之间的,电子密度保持两个原子在一起成键的。
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