So let's do a quick clicker question, and you tell me how many valence electrons does fluorine have? Remember, valence electrons are different from core, they're only the outer-most electrons in the outer-most shell.

那么让我们来做一个小选择题，请大家来告诉我,氟有多少个价电子，要记得，价电子与芯电子不同，它们是在最外壳层的最靠外面的电子。

麻省理工公开课 - 化学原理课程节选

If you want to understand whether compounds form or not look only at the valence shell.

如果你想理解化合物是否形成,而不仅仅只是看看价层。

麻省理工公开课 - 固态化学导论课程节选

So we actually only need two electrons to fill up the valence shell of hydrogen, remember that's because all we need to fill up is the 1 s.

我们其实只需要两个电子,就可以将氢的价壳层排满，要记得这是因为我们只需要排满，1，s，轨道。

麻省理工公开课 - 化学原理课程节选

Whatever the n number is, with the exception of helium, helium is the oddity because there's only two elements in n equals one shell.

无论n是多少，除了氦之外，氦是个特例,因为只有两个元素,在n为1的这一层。

麻省理工公开课 - 固态化学导论课程节选

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