外层外层，如树皮或果皮。

An external layer, such as bark or rind.

youdao

最后，恒星大气的最外层部分是日冕，这是一个由于外层对流导致的超热区域。

Finally, the outermost part of a star's atmosphere is the corona, which if super-hot might be linked with convection in the outer layers.

youdao

所有的稀有气体元素的最外层电子数都是该层最大的可能数目：氦的最外层电子有两个，其它的稀有气体最外层电子数是八。这使稀有气体非常稳定。

All noble gases have the maximum number of electrons possible in their outer shell (two for helium, eight for all others), making them highly stable.

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There is a huge difference between the energies in the outermost shell and the inner shells, which tells you that it's unlikely that any electrons except those in the outermost shell are going to be active.

最外层和最里层所具有的能量,有很大差异，而这告诉我们有一点是不太可能的,那就是除了最外层的电子,别的电子都是应该是活泼的。

麻省理工公开课 - 固态化学导论课程节选

So, for example, for sodium, we can instead write neon and then 3 s 1.

所以举例来说对于钠其他的外层电子，的结合的电子。

麻省理工公开课 - 化学原理课程节选

And, this outermost shell is termed the valence shell.

这个最外层被称作价电子层。

麻省理工公开课 - 固态化学导论课程节选