Question

What is a delocalized pi bond?

Answer 1

Hint: Delocalized pi bonds shared between all atoms in a molecule, they are spread out over more than two nuclei. . In a pi bond system the pi bond is not fixed with a particular atom and moves continuously due to conjugation.

Complete answer:
Delocalized pi bond is a bond in which electrons are free to move over more than two nuclei. Delocalization is the phenomenon by which electrons or bonds are transient in nature. In a delocalized pi bond, the pi system can exist in several conformations. An example of this kind of system is $ benzene $ . It has an alternating pi bond formation as it contains three double bonds inside a six-membered ring. These three double bonds can have different locations as there has to be a single bond between any two double bonds. Thus it is a delocalized system
One must be aware of the fact that pi bonds are between two unhybridized p-orbitals that are adjacent to each other. These two dumbbell-shaped p-orbitals are aligned with respect to each other such that the lobes of the orbitals overlap with each other. Now imagine this situation in more than two adjacent atoms. All of the unhybridized p-orbitals that are next to each other can overlap, and the electrons within these p-orbitals can be delocalized as they can extend out to more than two atoms rather than localized to two atoms from two p-orbitals overlappings.
Another example is $ ethylene $ where the electrons are not confined to a single atom. Before the p-orbitals overlap, the p-electrons are confined to each carbon atom. However, the electrons in the pi bond are free to roam over both carbon atoms.

Note:
pi-electrons are present in double bonds and sigma electrons are present in a single bond. Usually, pi-bond formation takes place after the sigma bond formation. $ benzene $ is a stable structure due to the delocalized pi bond system.