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Reference Notes | Science
Difference Between Sigma (σ) and Pi (π) Bond
Unit: Chemical Bonding and Shape of Molecules
Chemistry Class 12
Sigma (σ) bond: A covalent bond formed due to the overlapping of the orbitals of two atoms along the internuclear axis (orbital axis) is called sigma (σ) bond.
Pi (π) bond: A covalent bond formed by sideways (lateral) overlapping of two half-filled p-orbitals is called pi (π-bond).
Difference Between Sigma (σ) and Pi (π) Bond:
| Sigma (σ) Bond | Pi (π) Bond |
| 1. It is formed by the end on end (head on) overlap of two s or one s and one p-orbital along their internuclear axis. | 1. It is formed by the sideway overlapping of two p-orbitals and not obtained from hybrid orbitals. |
| 2. It determines the direction and extent of internuclear distance. | 2. It has no primary effect on the direction of bond but shortens the internuclear distance. |
| 3. It is a strong bond due to greater extent of internuclear distance. | 3. It is weak bond due to poor overlap of orbitals. It is formed when a σ-bond already exists between atoms. |
| 4. The molecular σ-orbital consists of a single electron cloud symmetrically around the internuclear axis. | 4. The molecular π-orbital consists of two electrons clouds, one above and one below the plane of bonded atoms. |
| 5. There can be free rotation of atoms around the sigma bond. | 5. As the electron cloud overlap is above and below the plane of atoms free rotation is not possible around the π-bond. |
