So, in talking about covalent bonds, we should be able to still apply a more general definition of a chemical bond, which should tell us that the h 2 molecule is going to be lower in energy than if we looked at 2 separate hydrogen atom molecules.

那么，既然提到了共价键，我们应该还可以,给化学键下一个更普遍的定义,那就是告诉我们氢分子能量应该更低,与两个分开的氢的单原子分子相比。

麻省理工公开课 - 化学原理课程节选

We have either single atoms or molecules consisting of small numbers of atoms.

单原子或者分子,由很多很小的原子组成。

麻省理工公开课 - 固态化学导论课程节选