So, how many distinct, so again, we're talking about distinct kinetic energies, a spectrum for the element hafnium, 72 and I'll tell you here that it has a z of 72, so you don't have to spend two minutes searching your periodic table.

好，有多少分立的……还是一样，我们讨论的还是不同的动能，铪元素的光谱中出现，而且我来告诉大家铪的原子序数是，这样你就不用因为在元素周期表中找它,而花费两分钟的时间了。

麻省理工公开课 - 化学原理课程节选