When we talk about resonance structures, we're talking about cases that have the same arrangement of atoms the key is the atoms are the same, and the thing that is different is the arrangement of electrons here.

当我们讨论共振结构的时候，我们讨论的是原子排布相同情况,关键在于原子是相同的，不一样的只是电子排布。

麻省理工公开课 - 化学原理课程节选