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

Krista Eberle, director of food safety programs at the Egg Safety Center, reiterated that only shell eggs are affected by the Wright County recall.

CNN: STORY HIGHLIGHTS

Only shell eggs are affected by the recall, the company said.

CNN: STORY HIGHLIGHTS

The Foreign Relations Committee is only a shell of what it was when the influential Arkansas Democrat was its chairman from 1959 to 1974.

CNN: Senator No