The number of sigma and pi bonds in a molecule of ethyne, C2H2, is
Correct answer: A. three sigma and two pi
- A. three sigma and two pi
- B. two sigma and three pi
- C. five sigma and no pi
- D. four sigma and one pi
Explanation
The two carbon to hydrogen bonds are sigma, and the carbon to carbon triple bond consists of one sigma plus two pi bonds, giving three sigma and two pi in total. The rule to apply is that a single bond is one sigma, a double bond one sigma and one pi, and a triple bond one sigma and two pi. Counting them correctly is what makes the hybridisation obvious as well.
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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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