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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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If we're talking about a single bond, we're talking about 2 orbitals overlapping in the internuclear axis.
如果我们讨论的是单键，我们讨论的是两个轨道,在核间轴中重叠。
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And the convention is that when two atoms bond, they bond along the z-axis.
我们的惯例是，两个轨道成键，键轴为Z轴。
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And a sigma bond forms any time you have two orbitals coming together and interacting on that internuclear axis.
当你把两个轨道合在一起,并在核间轴上有相互作用时,就形成了sigma键。
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Pi orbitals are a molecular orbital that have a nodal plane through the bond axis.
轨道是沿着键轴,有节面的分子轨道。
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Any time two orbitals come straight on together in that internuclear axis, you're going to have a sigma bond.
任何时候两个轨道,在核间轴上直接到一起，你就能得到sigma键。
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We're having two orbitals coming together on the bond axis.
我们在这个轴上有两个轨道相互靠近。
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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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But in sigma orbitals, you have no nodal planes along the bond axis, so if we had a nodal plane here, we'd see an area where the wave function was equal to zero.
但在sigma轨道里，沿着轴向是没有节点平面的，如果我们有个节点，我们就会看到某个地方波函数等于0。
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So, if we think about this z bonding axis between the two carbon atoms, we can picture overlap of those s p hybrid orbitals, and then we can also picture bonding to hydrogen.
如果我们考虑,两个碳原子之间的z成键轴，我们可以画出sp杂化轨道的交叠，我们也可以画出和氢原子的成键。
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The reason that it's a sigma bond is sp3 because the s p 3 hybrid orbital is directly interacting with the 1 s orbital of the hydrogen atom, and that's going to happen on the internuclear axis, they're just coming together.
它是sigma键的原因,是因为,杂化轨道直接和氢原子1s轨道相互作用，它们作用发生在核间轴上，它们会到一起。
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So what we can say is look at each of these separately, so if we start with looking at the 2 p z orbital, the highest probability of finding an electron in the 2 p z orbital, is going to be along this z-axis.
我们可以来分别看看这些图，首先来看看2pz轨道，在2pz轨道里,找到电子的最大概率，是沿着ｚ轴。
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But keep in mind sigma orbitals have no nodal planes along the bond axis.
但记住sigma轨道沿着,键轴方向是没有节点的。
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So again, we can name these molecular orbitals and these we're going to call also to point out there is now a bond axis along this nodal plane, which is something we didn't see before when we were combining the s orbitals.
同样的，我们可以,命名这些分子轨道,这些轨道叫做-同样要指出的是,现在沿着键轴是一个节点面，这是我们讨论s轨道的时候,从没有看到过的。
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There's not two bonds, that's one pi bond, and the reason is because it's 2 p orbitals coming together, and remember p orbitals have electron density above and below the axis, so when they come together, it kind of looks like one bonds, but essentially what we have here is one pi bond.
这不是两个键，这是一个π键，因为这是两个2p轨道组合而成的，记住p轨道在键轴之上,和键轴之下都有电子密度，当它们靠近时，这看着很像两个键，但本质上它是一个π键。
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Specifically, it's always the z that forms the sigma orbital, and the reason is at least at a minimum for this class we always define the internuclear axis as the z axis, so this is always the z axis, so it's always going to be the 2 p z's that are coming together head-on.
特别的，z总是形成sigma轨道，这是因为至少在这个课里面,我们总是定义核间轴为z轴，所以这总是z轴，所以2pz轨道总是,朝一个方向出现。
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