Covalent bonding:

The MOs are of dissimilar energies. One is more stable as compared to the original atomic orbitals and is termed as the bonding MO. Another is less stable and is termed as the antibonding MO. The bonding MO is shaped such as a rugby ball and results from the combination of the 1s atomic orbitals. Because this is the more stable MO, the valence electrons (one by every hydrogen) enter this orbital and pair up. The antibonding MO is of high energy and contains two deformed spheres. This remains empty. Because the electrons end up in a bonding MO that is more stable as compared to the original atomic orbitals, energy is released and bond creation is favored. In the consequent discussions, we shall concentrate solely on the bonding MOs to explain bonding and molecular shape, but it is significant to realize that antibonding molecular orbitals as well exist.