The interaction between π bond and lone pair of electrons present on an adjacent atom is responsible for

Solution

Chemistry ma’am · 3 steps

A lone pair sitting next to a π bond can spread into it, and that sharing of electrons is resonance.

1. What is interacting. A lone pair sits in a p orbital on an atom right next to a π bond. That p orbital lies parallel to the p orbitals of the π bond, so they overlap sideways.
2. Delocalisation. Because of this overlap, the lone pair and the π electrons spread over the whole system. In vinyl chloride, CH₂=CH-Cl, a lone pair on Cl moves in to form C=Cl and the π pair shifts onto the end carbon.

   CH₂=CH-Cl(..): ↔ ⁻CH₂-CH=Cl⁺

   Effect	What causes it
   Resonance	π bond conjugated with a lone pair or another π bond; permanent
   Electromeric	Full shift of a π pair, only while an attacking reagent is present
   Hyperconjugation	σ (C–H) bond overlapping with an adjacent π bond or empty p orbital
   Inductive	Pull or push of electrons through σ bonds, due to electronegativity

3. So. Lone pair and π bond conjugation is the resonance effect, option (a).

The idea to keep. Ask which electrons overlap with the π bond. A lone pair or another π bond gives resonance. A C–H σ bond gives hyperconjugation. σ bonds alone give the inductive effect.

Answer from the NTA final answer key. Solution by PrepWiser.