Sigma Molecular orbital () involves shared electron density directly in between the bonded atoms, along the axis.
It is formed by the head-to-head overlapping of atomic orbitals along the inter-nuclear axis.
It is formed independently. No involvement of the pi bond takes place.
They are comparatively stronger than a pi bond.
Sigma Molecular orbital () is formed by adding the two atomic orbitals together where represents the s atomic orbital of a molecule A and represents the s atomic orbital of a molecule B.
Sigma- star Molecular orbital () is formed by subtracting the two atomic orbitals. where represents the s atomic orbital of a molecule A and represents the s atomic orbital of a molecule B
This addition and subtraction of atomic orbitals is called Linear Combination of Atomic Orbitals (LCAO)