The second bond in ethyne is?
Correct answer: C. Pi bond between unhybridized orbitals
- A. Pi bond between hybridized orbitals
- B. Sigma bond between hybridized orbitals
- C. Pi bond between unhybridized orbitals
- D. Sigma bond between unhybridized orbitals
Explanation
Option A: Pi bond between hybridized orbitals: In molecular orbital theory, hybridized orbitals can overlap to form sigma bonds. However, pi bonds are formed by the overlap of unhybridized p orbitals. So, this option is not correct for the second bond in ethyne. Option B: Sigma bond between hybridized orbitals: Sigma bonds are formed by the head-on overlap of atomic orbitals. In ethyne, the first bond between the two carbon atoms is a sigma bond formed by the overlap of sp hybridized orbitals. However, the second bond in ethyne is a pi bond, not a sigma bond. Therefore, this option is not correct. Option C: The second bond in ethyne is a pi bond formed by the overlap of unhybridized p orbitals. The carbon atoms in ethyne have one unhybridized p orbital each, which align parallel to each other and form the pi bond. Option D: Sigma bond between unhybridized orbitals: Sigma bonds are formed by the head-on overlap of atomic orbitals, but in ethyne, the second bond is a pi bond, not a sigma bond. Therefore, this option is not correct.
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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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