<span>The answer to this question would be: placement of electrons only
An atom with resonance structure or mesomerism has one or more different structure with different placement of the electron. The atom should have a same amount of electron but only differ in the electron position. This will result in a different Lewis structure model. In this structure, you can find </span>π electrons pair.<span>
Recall that most atoms are stable when their outermost ring has eight electrons. (Some atoms, such as lithium and beryllium, are stable when their outermost ring has two electrons.)
