So, for example, if I have a sodium ion over here, and I have a chloride ion over here, where the distance from center to center r I'm denoting as r, this is nucleus to nucleus separation.

所以，比如这有一个钠离子，和一个氯离子，它们中心与中心间的距离,我把它设为，这是原子核和原子和的间距。

麻省理工公开课 - 固态化学导论课程节选

So, we can use Coulomb's force law to think and it does that, it tells us the force is a function of that distance. But what it does not tell us, which if we're trying to describe an atom we really want to know, is what happens to the distance as time passes?

来考虑这两个粒子之间的,它告诉我们力随距离的函数关系,但它不能告诉我们，而我们如果要描述,原子又非常想知道的是,距离随时间的变化时怎样的？

麻省理工公开课 - 化学原理课程节选

that's one way to think about it, and there's also another way, and this is the way that your book presents it. If you, in fact, have two of the same atom right next to each other, let's say you have a crystal, or let's say you're talking about a metal, what you can do is just look at the distance between the two nuclei, and split that in 1/2, and take the atomic radius that way.

这只是一种定义的思路，另外还有其它方法，也就是你们课本上的方法，如果你，事实上，有两个相同的原子彼此靠在一起，比如说你有一个晶体，或者说你讨论的是一个金属，你所要做的就是,看看这两个原子核之间的距离，然后将距离除以二，就得到了这个原子的半径。

麻省理工公开课 - 化学原理课程节选