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What is Resonance in Chemistry?

Resonance in Chemistry is otherwise called Mesomerism simply refers to the alternation or rotation of double bonds in some compounds which ensure their stability.

Resonance in Chemistry is a term used to describe the representation of the covalent bonding in some compounds like Benzene, Carbon IV oxide, and even Ozone.

Additionally, resonance exists in ions too for example in Carbonate ion (CO32-), nitrate ion (NO2-), and even in nitrate ion (NO3).

It is important to note that resonance is represented using hybrid structures called resonance or canonical structures.

By resonance or canonical structures, we mean Lewis structures of a molecule that have octet configurations but with different orientations of electrons. A single resonance structure is limited in describing the bonding in the resonance of a compound.

The delocalization of electrons in molecules is best explained using canonical structures that show the different positions of electrons in such molecules. Also, remember that the resonance structures are hybrids and differ only in the orientation or position of electrons and not in the position of atoms.

Before I show resonance in some compounds or molecules, it is crucial to mention that not every compound exhibits resonance.

How Do You Know if a Molecule has Resonance?

If a molecule exhibits resonance, then it cannot be represented with only one Lewis diagram because the electrons are moving and not completely fixed at a position.

Resonance simply shows the different structures that a molecule can possess or exhibit.

For a molecule to exhibit resonance it must have a double bond that is resonating i.e moving round.

Resonance in Chemistry in some compounds

7 Examples of Resonance (Mesomerism) in Compounds

Resonance in Ozone

Ozone exhibits resonance and this can be seen in the resonance structures. Resonance structures exist when one Lewis dot diagram cannot be used to explain resonance in compounds.

Resonance in Benzene

This is an example of resonance in Organic Chemistry. Benzene according to August Kekule has resonance or mesomeric structures that can illustrate the resonance in Benzene.

Explanation of Resonance in Benzene with diagram

The bonds are not fixed but delocalized and are always in constant movement to ensure the stability of the compound.

Resonance in H3PO3

This is a structure that can be shown using resonance structures.

 Explanation of resonance in H3PO3 with diagram

  • Resonance in Dinitrogen I oxide (N2O)
  • Resonance in Nitrogen IV oxide (NO2)
  • Resonance in dintrogen V oxide (N2O5)
  • Resonance in Benzoic acid

Examples of Resonance in ions

  1. Resonance in nitrate ion (NO3)
  2. Resonance in Perchlorate ion (ClO3)
  3. Resonance in Carbonate ion (CO32-)
  4. Resonance in Phosphate ion (PO43-)
  5. Resonance in Nitrite ion (NO2)

Resonance Structure Chemistry Notes

Resonance is a phenomenon that is shown in some compounds based on the fact that some compounds cannot be shown using one resonating structure.

So to illustrate the structures of some resonance compounds, more than one resonating structure will be required to illustrate this resonance.

In all the resonance structures, you will notice that the double bond is always in different locations in all the resonance structures.

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