But a real key in looking at these plots is where we, in fact, did go through zero and have this zero probability density.

是我们经历这些零值,而且有这些零概率密度,我们把它叫做节点。

麻省理工公开课 - 化学原理课程节选

And one common way to think about it, is to think about the value of r, or the radius, below which 90% of that electron density is going to be contained.

而通常的想法，是想象，r，的值，也就是半径的值，即有百分之九十的电子密度,都落在这个范围之内。

麻省理工公开课 - 化学原理课程节选