This should make a lot of sense, because we know that a hydrogen has 1 s as it's outer-most or valence orbital, so it can be filled up just with two 1 s electrons.

这也是很合理的，因为我们,知道氢只有，1，s，轨道,这就是它最外层的轨道或者说价轨道，因此只要两个，1，s，电子就可以将它填满。

麻省理工公开课 - 化学原理课程节选

So basically, that means one electron in an s orbital in their outer-most most shell.

因此基本上,这意味着那个在，s，轨道上价电子是最外层的。

麻省理工公开课 - 化学原理课程节选