This should make sense to you, because they don't, in fact, want to gain another electron, because that would mean that electron would have to go into a new value of n, a new shell, and that's really going to increase the energy of the system.

这对大家来说应该容易理解，因为它们实际上不想得到另一个电子，因为这意味着这个电子不得不,到一个新的，n，值更大的壳层上去，这将会增加系统的能量。

麻省理工公开课 - 化学原理课程节选

And the reason is simply because the energy that Z we gain in terms of moving up in z, 5 so from going to z equals 4 to z equals 5, -- is actually outweighed by the energy it takes to go into this new shell, to go into this new sub shell.

原因很简单,就是因为我们通过提升，所得到的能量--从，Z，等于，4，到，Z，等于，事实上比填充到这个新的壳层,新的亚壳层，所消耗的能量更多。

麻省理工公开课 - 化学原理课程节选