Atoms, bonding and types of reactions

Ethane

For Carbon-Carbon bond formation, consider ethane, C₂H₆. As before, each Carbon atom undergoes hybridisationhybridisation
The process by which different atomic orbitals mix and form new hybrid orbitals with their own energies and shapes, different to the original orbitals. giving four sp³ orbitals for the formation of four bonds.

Each Carbon atom bonds to three Hydrogens. As before, each Hydrogen 1s orbital merges with a Carbon sp³ orbital to give a σ-bond. As there are three Hydrogens to bond with each Carbon, one of the four sp³ orbitals remains for each Carbon.

The remaining hybrid orbitals, one on each Carbon, undergo end-to-end overlap with each other to give a new molecular bonding orbital. Again, this merging produces a σ-bond with two electrons shared within it.

It is important to note that there is free rotation around σ-bonds as it does not compromise the end-to-end overlap required for bonding.