And he found that the middle member of the triad had an atomic mass that was midway between the atomic masses of the end members.

他发现三元组中间的元素,的原子质量,是位于两端的元素的原子质量,的中间。

麻省理工公开课 - 固态化学导论课程节选

If you add all these up then you end up 011 with 12.011 as the atomic mass.

如果你将这些都加起来，你会得出,原子质量是12。

麻省理工公开课 - 固态化学导论课程节选