I would say with the aid of an energy level diagram explain the fact that helium is found as atomic gas and not molecular. How about this one?

我要说的是，在能级图的帮助下,可以解释氦气是单原子气体,而不是分子气体这一事实,那么这个呢？

麻省理工公开课 - 固态化学导论课程节选