Sigma (𝞂) bond

Sigma (𝞂) bond

This type of covalent bond is formed by the end to end (hand-on) overlap of bonding orbitals along the internuclear axis. This is called as head on overlap or axial overlap. This can be formed by any one of the following types of combinations of atomic orbitals.

s-s overlapping : In this case, there is overlap of two half filled s-orbitals along the internuclear axis as shown below:
s-s overlapping, sigma bond

s-p overlapping: This type of overlapping occurs between half filled s-orbitals of one atom and half filled p-orbitals of another atom.
s-p overlapping, sigma bond

p-p overlapping : This type of overlap takes place between half filled p-orbitals of the two approaching atoms.

p-p overlapping, sigma bond