Molecular Orbital Diagram

Molecular orbital diagram is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the linear combination of atomic orbitals (LCAO) method in particular.

Molecular orbital diagram is a molecular orbital energy levels diagram, shown as short horizontal lines in the center, flanked by constituent atomic orbital energy levels through dotted lines for comparison, with the energy levels increasing from the bottom to the top. Degenerate energy levels are commonly shown side by side. Appropriate atomic orbital and molecular orbital levels are filled with electrons by the Pauli Exclusion Principle, symbolized by small vertical arrows whose directions indicate the electron spins.
Bond order can easily be calculated by Moleculat Orbital Diagram by the following formula-
Bond Order = 1/2(Bonding Electrons − Antibonding Electrons)

Bonding Molecular Orbital

Bonding molecular orbitals are formed by the combination of atomic orbitals. It has lower energy than that of atomic orbitals from which it is formed.
Electron charge density in between the nuclei is high and hence the repulsion between the nuclei is very low and thus the BMO favours the stable bond formation.

Anti Bonding Molecular Orbital

Antibonding molecular orbitals are formed by the subtraction of atomic orbitals. It has higher energy than that of atomic orbitals from which it is formed.
Electron charge density in between the nuclei is low thus the ABMO does not favours the bond formation.