Question
Distinguish between a sigma (σ) bond and a pi 
bond.
Solution
| Sigma (σ) bond |  bond |
| 1. It is formed by the coaxial overlapping of two half filled atomic orbitals along the internuclear axis. | 1. It is formed by the sidewise or lateral overlapping of two half filled p-orbitals perpendicular to the intranuclear axis. |
| 2. This bond can be formed by the overlap of s –s.s –p and p-p orbitals. | 2. It involves the overlap of p-orbitals only i.e. s orbitals can not participate in the formation of  the bond. |
| 3. Sigma bond is stronger and less reactive. | 3.  bond is weaker and more reactive. |
| 4. They have cylindrical symmetry of electron density about the bond axis. | 4. Electron density is localised above and below the plane of the bond axis. |
| 5. Free rotation about a σ-bond is possible. | 5. Rotation of bond is restricted. |
| 6. Sigma bonds have an independent existence. | 6. -bond exist along with a σ bond. |
