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

A. C2H2


B. C2H4



There are three sigma’s and two pi-bonds in C2H2.

Explanation: A single bond is a result of the axial overlap of bonding orbitals. Hence, it contributes a sigma bond. A multiple bond (double or triple bond) is always formed as a result of the sidewise overlap of orbitals. A pi-bond is always present in it. A triple bond is a combination of two pi-bonds and one sigma bond.


B.



There are five sigma bonds and one pi-bond in C2H4.


Explanation: A single bond is a result of the axial overlap of bonding orbitals. Hence, it contributes a sigma bond. A multiple bond (double or triple bond) is always formed as a result of the sidewise overlap of orbitals. A pi-bond is always present in it. A triple bond is a combination of two pi-bonds and one sigma bond.


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