Question

How do you determine the number of pi and sigma bonds in a structure and locate them?

Answer 1

Hint : If the atomic orbitals overlap head-on positive along the internuclear axis, then sigma bonds are formed. If the atomic orbitals overlap sideways positively along a direction that is perpendicular to the internuclear axis, then pi bonds are formed.

Complete Step By Step Answer:
Sigma bonds and pi bonds are different types of covalent bonds which differ in terms of overlapping of the atomic orbitals. Sigma bonds are formed as a result of head to head overlapping of the atomic orbitals. Pi bonds are formed as a result of lateral overlapping of two atomic orbitals. During the formation of pi bonds, the axes of atomic orbitals are parallel to each other but overlapping is perpendicular to the internuclear axis. The sigma bonds are the strongest covalent bonds because of the direct overlapping of the participating orbitals. Pi bonds are usually weaker than the sigma bonds because of the lower degree of overlapping. To determine the number of sigma and pi bonds in a structure, first draw down the extended structure. Then count every single bond as a sigma bond. If there is a double bond, one of the bonds will be a sigma bond and another bond will be a pi bond. If there is a triple bond, one of the three bonds will be a sigma bond and the other two bonds will be pi bonds.

Note :
Note that single bonds present in between atoms are always sigma bonds. One double bond consists of one sigma bond and the other bond is a pi bond. One triple bond consists of one sigma bond and two pi bonds. Drawing the extended structure will help us to count the number of sigma and pi bonds easily.