I want to point out that the zero energy is defined as when you have a naked proton -- where the electron has popped out -- that's what we've defined as zero energy up to this point when we're talking about single atoms.

我想指出，这里零点能的定义,是当我们只有一个裸露的质子,而没有电子时-,到目前为止对零点能一直采用这样的定义,当我们在讨论单个原子时。

化学原理课程节选 : 麻省理工公开课