One way to think about it, if we want to use a classical analogy, which often helps to give us an idea of what's going on, is the spin of an electron, we can picture it rotating on its own axis.

如果我们用一个，经典的比喻来考虑它的话，这经常会帮助我们建立起一些概念，就是我们可以把电子的，自旋想象是它绕着轴自转。

麻省理工公开课 - 化学原理课程节选

The first one will be above and below the bond axis is where we'll see the electron density, and the second will be perpendicular to that, so it will be a density in front of and behind the bond axis.

第一个是在键轴之上和之下,我们可以看到电子密度，另外一个垂直于它，所以在键轴之前和之后有电子密度。

麻省理工公开课 - 化学原理课程节选

Because already I can see there is a line of sight from one nucleus to the other with no electron density whatsoever.

因为我已经看出在Z轴,有一条线从这个核到那个核,没有连续电子。

麻省理工公开课 - 固态化学导论课程节选

So pi bonds have electron density both above and below the bond axis, but they actually have a nodal plane at this z, this bond axis here.

键在键轴之上,和之下都有电子密度，但它们在z方向有节面，这是键轴的地方。

麻省理工公开课 - 化学原理课程节选

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。

麻省理工公开课 - 化学原理课程节选

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。

麻省理工公开课 - 化学原理课程节选