Question

How would you distinguish between a sigma bond and a pi bond?

Short answer

Sigma and Pi bonds can be distinguished based on their formation, stability, rotation, and overlapping. Sigma bonds are formed by direct overlapping of atomic orbitals, they are stronger and allow free rotation because they are symmetrical. Pi bonds, on the other hand, are formed by sideways overlapping of atomic orbitals, they are weaker and don't allow free rotation because they are not symmetrical.

Step-by-step solution

Definition of Sigma Bond

A sigma bond is the strongest type of covalent bond in which the atomic orbitals directly overlap between the nuclei of two atoms. They are formed by the end-to-end overlapping of atomic orbitals. Sigma bonds allow for free rotation because they are symmetrical.

Definition of Pi Bond

A pi bond is a covalent bond that is formed by the sideways overlapping of atomic orbitals. The overlapping takes place above and below the plane of the atoms. Unlike sigma bonds, pi bonds do not allow for free rotation because they are not symmetrical.

Distinguishing Sigma and Pi bonds

Sigma bonds are always the first bonds to be formed between atoms and can exist independently, while pi bonds are formed over and above sigma bonds and cannot exist independently. Furthermore, a sigma bond is stronger and more stable compared to a pi bond due to the greater extent of overlap, which forms a stronger electrostatic force of attraction. Another distinguishing feature is in their shapes: sigma bonds are symmetrical along the line connecting the two nuclei, whereas pi bonds are not.