Resonance:

All atoms must be in the same position - only electrons and bonds move around

Draw ALL possible structures and arrows between structures

Resonance is a concept in chemistry that describes the delocalization of electrons within a molecule or an ion. It occurs when a molecule or ion can be represented by multiple Lewis structures, each differing in the placement of electrons. These different Lewis structures, called resonance structures, contribute to the overall structure and properties of the molecule or ion.

Resonance arises when there are multiple ways to arrange electrons in a molecule due to the presence of pi bonds (double or triple bonds), lone pairs, or delocalized electron systems. The resonance structures are represented using double-headed arrows between them, indicating that the actual electronic structure is a hybrid of the contributing resonance structures.

One of the key features of resonance is that it stabilizes the molecule or ion. The delocalization of electrons leads to the spreading out of electron density, which results in increased stability. This stability arises from the equalization of bond lengths and bond strengths within the molecule or ion.

Resonance also affects the reactivity and chemical behavior of molecules or ions. It influences factors such as acidity, basicity, and the ability to undergo nucleophilic or electrophilic reactions. Resonance stabilization can impact the overall stability of reactive intermediates, such as carbocations or radicals.