It makes a lot of sense when we look at it energetically, because if we think about a 1 s core electron, that's going to be held really, really tightly to the nucleus.

从能量的观点来看这是非常合理的，因为如果我们考虑一下，1，s，芯电子，它会被原子核束缚得非常非常紧。

麻省理工公开课 - 化学原理课程节选

Core electrons are all those electrons held in really tight with the nucleus in the inner shells, whereas the valence electrons are only those electrons that are in the outer-most shell, or at your highest value of n of the principal quantum number.

芯电子是那些,在内壳层被原子核束缚得非常紧的电子，而价电子只包括,最外层的电子，或者说主量子数，n，的值最大的那些电子。

麻省理工公开课 - 化学原理课程节选