r+ And let's say that sodium has a radius, r plus, r- and chlorine has a radius, r minus, when r is very large in comparison to the radii of the ions, I don't need to draw them this way.

让我们假设钠有半径，是，氯也有半径，是，当r比离子半径大很多的时候，我不需要这样来描述。

麻省理工公开课 - 固态化学导论课程节选