What is Sigma Bond ?

According to Valance bond theory (VBT) by overlapping of atomic Orbitals three types of covalent bond formation take place.

(1) Sigma Bond:

(2) Pi Bond:

(3) Delta Bond:

Sigma Bond: 

(1)The sigma bond formed by nuclear/head on/axial overlapping /end to end overlap of pure as well as hybrid atomic orbitals.

(2) Sigma bond do not involve in resonance.

(3) free rotation is possible about a single sigma bond.

(4) Maximum overlapping is possible between electron clouds and hence it is strong bond.

(5) There can be only sigma bond between two atoms and sigma bond are formed by three type of overlapping.

(A) S-S overlapping: Two half filled s-orbitals overlap along inter nuclear axis for example H₂ molecule.

(B) s-p overlapping : When half filled s-orbital of one atom overlap with half with p-orbital of other atom for example HF molecule.

(C) p-p overlapping (Coaxial overlapping): it involves the coaxial overlapping between half filled p-orbitals of two different atoms for examples F₂, Cl₂, Br₂ etc

What is Pi-(π)Bond ?