Answer:
Resonance
Explanation:
Resonance is an idea in chemistry that is used to explain such properties as equal bond lengths, bond angles and some other chemical behaviours. Resonance structures show the possible distribution of electrons in molecules. All the contributing canonical or resonance structures give a clue regarding the true structure of the chemical specie under consideration.
The true structure of the specie is somewhere in between that of all the contributing canonical structures. Resonance is often employed to explain properties such as equal bond lengths and bond angles just as typified in the question under consideration.