So what is actually going to matter is how closely that electron can penetrate to the nucleus, and what I mean by penetrate to the nucleus is is there probability density a decent amount that's very close to the nucleus.

所以实际上有关系的是,电子可以穿越至原子核有多近,我所指的穿越至原子核是,这里有一定数量的概率密度,可以距离原子核非常近。

麻省理工公开课 - 化学原理课程节选

And when we look at this, it's actually split by what's called a nodal plane, which is pointed out in light orange here on this picture, but what we just mean is that there is this whole plane that separates the two lobes where there is absolutely no electron density.

我们来看这里，实际上它被一个节面分开，在这图里用淡黄色表示，这意味着这个分开,两个叶瓣的平面上,是完全没有电子密度的。

麻省理工公开课 - 化学原理课程节选