The acetylene molecule contains:___________?
Correct answer: C. 3 sigma and 2 pi bonds
- A. 5 sigma bonds
- B. 4 sigma and 1 pi bonds
- C. 3 sigma and 2 pi bonds
- D. 2 sigma and 3 pi bonds
Explanation
Acetylene has the structure H-C≡C-H. Each C-H bond is one sigma bond, and the carbon-carbon triple bond contains one sigma bond plus two pi bonds, giving 3 sigma bonds and 2 pi bonds in total. The likely mistake is choosing 4 sigma and 1 pi, which treats a triple bond as if it contained only one pi bond.
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About Sigma and Pi Bonds
A sigma bond forms by direct end-to-end overlap along the internuclear axis, whereas a pi bond forms by sideways overlap of parallel orbitals. The topic covers single, double and triple bonds, bond composition, restricted rotation and the relation between sigma and pi bonding and orbital hybridisation.
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