what is the difference b/w resonance and conjugation??

Resonance and conjugation are interrelated. If there is conjugation in a molecule, we can draw resonance structures to it by alternating the pi bonds. Since the pi electrons are delocalized in the whole conjugated system, all the resonance structures are valid for such molecule
Resonance allows a conjugated system to delocalize electrons.
conjugation:-

In a molecule when there is alternating single and multiple bonds present, we say that the system is conjugated. For example, benzene molecule is a conjugated system. In a multiple bond, there is one sigma bond and one or two pi ponds. Pi bonds are made up by overlapping p orbitals. The electrons in the p orbitals are located perpendicular to the plane of the molecule. So when there are pi bonds in alternating bonds, all the electrons are delocalized throughout the conjugated system.
resonance:
By having the atoms share or transfer electrons, we try to give each atom the noble gas electronic configuration. However, in this attempt, we may impose an artificial location on the electrons. As a result, more than one equivalent Lewis structures can be written for many molecules and ions. The structures written by changing the position of the electrons are known as resonance structures.

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Aarti Gupta
askIITian Faculty