What is the Difference Between Sigma and Pi Molecular Orbitals?
🆚 Go to Comparative Table 🆚Sigma and pi molecular orbitals are two types of molecular orbitals that contribute to the actual structure of a chemical compound and are responsible for the formation of covalent bonds. The key differences between sigma and pi molecular orbitals are:
- Formation: Sigma molecular orbitals are formed by the head-to-head overlapping of atomic orbitals along the line joining the two nuclei, resulting in a strong covalent bond. Pi molecular orbitals, on the other hand, are formed from the lateral or parallel overlap of atomic orbitals.
- Overlapping Orbitals: Sigma orbitals can be pure or hybrid, while pi orbitals must be unhybridized.
- Bond Strength: Sigma bonds are generally stronger than pi bonds due to the direct overlapping of the participating orbitals.
- Electron Participation: The electrons participating in a sigma bond are commonly referred to as sigma electrons. In a double bond, there is one sigma bond and one pi bond, whereas a typical triple bond is made up of two pi bonds and one sigma bond.
In summary, sigma molecular orbitals are formed by the head-to-head overlapping of atomic orbitals, resulting in strong covalent bonds, while pi molecular orbitals are formed by the parallel overlap of atomic orbitals, resulting in weaker covalent bonds.
Comparative Table: Sigma vs Pi Molecular Orbitals
Sigma and pi molecular orbitals are two types of molecular orbitals that contribute to the formation of single and double or triple bonds, respectively. Here is a table comparing the differences between sigma and pi molecular orbitals:
| Sigma Molecular Orbitals | Pi Molecular Orbitals |
|---|---|
| Form from the overlapping of atomic orbitals in a parallel direction | Form from the overlapping of atomic orbitals in a perpendicular direction |
| Have cylindrical symmetry, with bond length forming a circle in any cross-sectional plane | Have planar symmetry, with electron density concentrated above and below the nucleus plane |
| Responsible for the formation of single bonds | Responsible for the formation of double and triple bonds |
| Lower in energy than pi molecular orbitals | Higher in energy than sigma molecular orbitals |
| Examples: σs and σp orbitals | Examples: πp and πd orbitals |
In a molecule with a double bond, such as ethene (H2C=CH2), the pi orbital is formed by combining p atomic orbitals of like sign using "side-on" overlap, resulting in a pi (Ï€) bonding molecular orbital. In contrast, a sigma bond is formed by the overlapping of atomic orbitals in a parallel direction, such as the overlapping of s and p atomic orbitals.
- Sigma vs pi Bonds
- Molecular Orbital vs Atomic Orbital
- Pure vs Hybrid Orbitals
- Px Py vs Pz Orbitals
- Bonding vs Antibonding Molecular Orbitals
- Molecular Orbital Theory vs Valence Bond Theory
- 1s vs 2s Orbital
- Hybrid vs Degenerate Orbitals
- Molecular Orbital Theory vs Hybridization Theory
- Orbit vs Orbital
- Atomic Orbital vs Hybrid Orbital
- Sigma Factor vs Rho Factor
- Spin vs Orbital Angular Momentum
- Molecular Geometry vs Electron Geometry
- Hybridized vs Unhybridized Orbitals
- dπ-dπ Bond vs Delta Bond
- Electron Pair Geometry vs Molecular Geometry
- Orbital Diagram vs Electron Configuration
- Trigonal Planar vs Trigonal Pyramidal