这个想法是由化学中的化学键理论想到的。在这个理论里，人们通常认为原子中形成满壳层的电子对化学键完全没有贡献。

The idea was suggested by the chemical theory of valency in which one is used to the idea of electrons in an atom forming closed shells which do not contribute at all to the valency.

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遗憾的是，一秒钟的标准定义依赖于原子在绝对零度的条件，而实际的时钟需要在室温下运行，室温条件下电子壳层膨胀了。

Unfortunately, the standard definition of a second relies on what the atom does at a temperature of absolute zero. Real clocks need to run at room temperature, where the shell of electrons puffs up.

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而对于氟来说，氟原子更小,与外部壳层在这的负一价氟离子相比。

Whereas for fluorine, fluorine is smaller than f minus is the one that's the outer shell shown here.

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Step three in our Lewis structure rules is to figure out how many electrons we would need in order for every single atom in our molecule to have a full valence shell.

路易斯结构规则的第三步是,找出让分子中每个原子的价壳层,都排满应该需要多少个价电子。

麻省理工公开课 - 化学原理课程节选

So as we go down we're now adding electrons to further and further away shells, so what we're going to see is that the atomic radius is going to increase as we're going down the periodic table.

当我们向下走时,我们会将电子加在越来越远的壳层上，因此我们将看到原子半径,将随我们沿周期表向下走而增大。

麻省理工公开课 - 化学原理课程节选

We're saying the probability of from the nucleus in some very thin shell that we describe by d r.

某一非常薄的壳层dr内,一个原子的概率,你想一个壳层时。

麻省理工公开课 - 化学原理课程节选