Sigma-bond and its Formation
Examples of sigma bonds are given below:
H H , H F , F F
The S P orbitals overlap of hydrogen and fluorine atoms give sigma-bond in hydrogen fluoride.
Pi-bond and its Formation
This bond is formed only when the two half filled co-planer p-orbitals overlapped in sideways manner such that the chances of finding the electrons is maximum perpendicular to the line joining the two nuclei is called a pi-bond. A pi-bond is formed only when the two atoms are already bonded by a sigma-bond.
Example of pi-bond in ethene is given below: