| List I | List II |
|---|---|
| A. C₂H₄ | I. 3 σ bonds, 2 π bonds |
| B. C₂H₂ | II. 3 σ bonds, one lone pair |
| C. CH₄ | III. 4 σ bonds |
| D. NH₃ | IV. 5 σ bonds, 1 π bond |
Solution
Core Logic
Let's analyze the bonding structure for each molecule: (A) C₂H₄ (Ethene): H₂C=CH₂. The C=C double bond has 1 σ and 1 π bond. Four C-H bonds are 4 σ bonds. Total: 5 σ, 1 π. (Matches IV) (B) C₂H₂ (Ethyne): HC ≡ CH. The C ≡ C triple bond has 1 σ and 2 π bonds. Two C-H bonds are 2 σ bonds. Total: 3 σ, 2 π. (Matches I) (C) CH₄ (Methane): Four single C-H bonds. Total: 4 σ. (Matches III) (D) NH₃ (Ammonia): Central N has 3 single N-H bonds and 1 lone pair. Total: 3 σ, 1 lone pair. (Matches II)
Step 1: Final Match
A arrow IV B arrow I C arrow III D arrow II
Pattern Recognition
Every single bond is a sigma (σ). Every double bond adds one pi (π). Every triple bond adds two pi (π) bonds. Ammonia's distinguishing feature is the explicit lone pair presence.
Chapter Mix
Class 11 Chemistry: Chemical Bonding and Molecular Structure