π What is a Sigma Bond?
A sigma bond (Ο bond) is the strongest type of covalent chemical bond. It is formed by head-on overlapping between atomic orbitals. This direct overlap results in a high electron density along the internuclear axis.
- βοΈ A sigma bond is the first bond formed between two atoms.
- πͺ Sigma bonds are generally stronger than pi bonds.
- π Sigma bonds allow for free rotation around the bond axis.
π§ͺ What is a Pi Bond?
A pi bond (Ο bond) is a covalent chemical bond where two lobes of one involved atomic orbital overlap two lobes of the other involved atomic orbital. This overlap occurs laterally (side-by-side) above and below the internuclear axis.
- π A pi bond is formed after a sigma bond has already been established.
- π Pi bonds are generally weaker than sigma bonds.
- π Pi bonds restrict rotation around the bond axis.
π Sigma vs. Pi Bonds: A Detailed Comparison
| Feature |
Sigma Bond (Ο) |
Pi Bond (Ο) |
| Formation |
Head-on overlap of atomic orbitals |
Lateral (side-by-side) overlap of p-orbitals |
| Overlap Region |
Concentrated along the internuclear axis |
Above and below the internuclear axis |
| Strength |
Stronger |
Weaker |
| Electron Density |
Higher along the internuclear axis |
Lower along the internuclear axis |
| Bond Order |
Single bond |
Contributes to double or triple bonds |
| Rotation |
Free rotation around the bond axis |
Restricted rotation around the bond axis |
| Energy |
Lower energy |
Higher energy |
π Key Takeaways
- 𧱠Sigma bonds are the foundation of chemical bonds, providing the initial and stronger link between atoms.
- β Pi bonds add to the bond order, creating double and triple bonds and influencing molecular properties.
- βοΈ The combination of sigma and pi bonds determines a molecule's shape, reactivity, and stability.
