So, basically what he's showing in these cubes is that there are eight spaces that need to be filled up to have a full cube.

因此，基本上他在这里展示是这些立方体中一共有,八个位置，需要把它们都填满才得到一个完整的立方体。

麻省理工公开课 - 化学原理课程节选

I don't care how you do it on exams or on problem sets, but you do need to be aware that the 3 d once filled is lower in energy than the 4 s, and the reason you need to be aware of that is if you're asked for the electron configuration now of the titanium ion.

我不关心你们在考试或者,问题集中如何做它，但是你们的确需要知道3d一旦被填充,它的能量是小于4s的，你们需要知道这个的原因,是如果你现在被要求,写出钛离子的电子构型。

麻省理工公开课 - 化学原理课程节选