Difference between sigma (σ) bond and pi (π) bond:
| Sigma (σ) bond | Pi (π) bond |
|---|---|
| It is formed by the axial (head-on) overlap of atomic orbitals. | It is formed by the sidewise overlap of atomic orbitals. |
| The overlapping orbitals lie along the internuclear axis. | The overlapping orbitals lie above and below the internuclear axis. |
| Electron density is concentrated between the two nuclei. | Electron density is concentrated in two regions on either side of the nuclei. |
| It is a stronger bond due to greater overlap. | It is a weaker bond due to less effective overlap. |
| It allows free rotation of bonded atoms. | It restricts free rotation of bonded atoms. |
| It can be formed by overlap of s–s, s–p, or p–p orbitals. | It is formed only by overlap of parallel p-orbitals. |
| Every single bond contains one σ bond. | A π bond is present only in double or triple bonds. |