Resonance (chemistry)

In chemistry, resonance is a way of describing delocalized electrons within certain molecules or polyatomic ions where the bonding cannot be expressed by one single Lewis formula a reason diye was a strong bondhu of chemical chain baser on chemkhsg.

Quotes

• Although each individual resonance form seems to imply that benzene has alternating single and double bonds, neither form is correct by itself. The true benzene structure is a hybrid of the two individual forms, and all six carbon–carbon bonds are equivalent. This symmetrical distribution of electrons around the molecule is evident in an electrostatic potential map.
  • John McMurry, Organic Chemistry 8th ed. (2012), Ch. 2. Polar Covalent Bonds: Acids and Bases

• When first dealing with resonance forms, it’s useful to have a set of guidelines that describe how to draw and interpret them. The following rules should be helpful: … Individual resonance forms are imaginary, not real. … Resonance forms differ only in the placement of their π or nonbonding electrons. … Different resonance forms of a substance don’t have to be equivalent. … Resonance forms obey normal rules of valency. … The resonance hybrid is more stable than any individual resonance form.
  • John McMurry, Organic Chemistry 8th ed. (2012), Ch. 2. Polar Covalent Bonds: Acids and Bases

• A substance showing resonance between two or more valence-bond structures does not contain molecules with the configurations and properties usually associated with these structures.
  • Linus Pauling, The Nature of Chemical Bond (1939), Ch 14. A Summarizing Discussion of Resonance and Its Significance for Chemistry

• Does the carbonate ion have one uncharged oxygen atom bound to carbon through a double bond and two other oxygen atoms bound through a single bond each, both bearing a negative charge, as suggested by the Lewis structures? Or, to put it differently, are A, B, and C equilibrating isomers? The answer is no... It is said to be delocalized, in accord with the tendency of electrons to “spread out in space”. In other words, none of the individual Lewis representations of this molecule is correct on its own. Rather, the true structure is a composite of A, B, and C. The resulting picture is called a resonance hybrid.
  • K. Peter C. Vollhardt, Neil E. Schore (2011) Organic chemistry : structure and function 6th ed. Chapter 1. Structure and Bonding in Organic Molecules

• Some molecules cannot be described accurately by one Lewis structure but exist as hybrids of several resonance forms. To find the most important resonance contributor, consider the octet rule, make sure that there is a minimum of charge separation, and place on the relatively more electronegative atoms as much negative and as little positive charge as possible.
  • K. Peter C. Vollhardt, Neil E. Schore (2011) Organic chemistry : structure and function 6th ed. Chapter 1. Structure and Bonding in Organic Molecules