Sigma Bonds
Definition and meaning of Sigma Bonds in chemistry.
Sigma bonds are the strongest type of covalent chemical bond, formed by the direct head-on overlapping of atomic orbitals directly along the internuclear axis. They always represent the first single bond formed between any two bonded atoms in a molecule.
In more detail
Because the electron density is highly concentrated directly in the space between the two positively charged atomic nuclei, sigma bonds feature maximum orbital overlap and are consequently very chemically stable. They can be formed from the simple overlap of two s orbitals, an s and a p orbital, two p orbitals, or various hybridized orbitals like sp3 or sp2. A critical feature of a single sigma bond is that free, unhindered rotation can occur around the bond axis at room temperature, which heavily influences molecular geometry and differs fundamentally from rigid double or triple bonds.
Key facts
| Field | General Chemistry |
|---|---|
| Formula | C2H6 |
| Overlap type | Head-on orbital overlap |
| Rotation | Allows free molecular rotation |
The single covalent bond between the two adjacent carbon atoms in an ethane molecule (C2H6) is a classic example of a strong sigma bond.
Frequently asked questions
Are sigma bonds generally stronger than pi bonds?
Yes, sigma bonds are significantly stronger than pi bonds because of the more direct and effective end-to-end orbital overlap along the axis.