Question

What is the total number of sigma and pi bonds in the following molecules?

1. \(C_2H_2\) 
2. \(C_2H_4\)

Answer 1

(i) C₂H₂

Structure of C₂H₂ (ethyne):

H — C ≡ C — H

• One C≡C triple bond consists of 1 σ bond and 2 π bonds
• Two C—H single bonds consist of 2 σ bonds

Total number of σ bonds = 3
Total number of π bonds = 2

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(ii) C₂H₄

Structure of C₂H₄ (ethene):

H₂C = CH₂

• One C=C double bond consists of 1 σ bond and 1 π bond
• Four C—H single bonds consist of 4 σ bonds

Total number of σ bonds = 5
Total number of π bonds = 1

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Final Answer:

C₂H₂ → σ = 3, π = 2
C₂H₄ → σ = 5, π = 1