It's kind of ironic that we put this in the same lecture as we talk about atomic radii, which we also call r, but they're two different r's, so you need to keep them separated in terms of what you're talking about.

有点讽刺的是,我们在同一堂课里还讨论过了原子半径，它也是用，r，表示的，但是它们具有不同的意义，因此大家需要注意区分它们,弄清楚我们讨论的是哪一个。

麻省理工公开课 - 化学原理课程节选