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Bonding Molecular Orbitals, types, formation, examples, factors and applications

November 1, 2023
written by shahzad haider

What are bonding molecular orbitals

In the hypnotic world of chemistry, molecular orbitals (MOs) arrange the movement of electrons, defining the unique characteristics of molecules. Among these, bonding molecular orbitals (BMOs) play a pivotal role, bringing atoms together in a harmonious embrace.

This article delves into the essence of bonding molecular orbitals, exploring their types, formation, and the significant role they play in predicting and understanding the properties of molecules.

Also read: Difference between bonding molecular orbitals and anti-bonding molecular orbitals

Types of Bonding Molecular Orbitals

Sigma (σ) Bonding Molecular Orbitals

Sigma-bonding molecular orbitals result from the head-to-head overlap of atomic orbitals along the internuclear axis. They are symmetrical to this axis and contribute significantly to the strength and stability of a bond.

Pi (π) Bonding Molecular Orbitals

Pi bonding molecular orbitals arise from the sideways overlap of atomic orbitals above and below the internuclear axis. These orbitals are often associated with double and triple bonds, adding an extra layer of stability to molecular structures.

Formation of Bonding Molecular Orbitals

Overlap of Atomic Orbitals

The formation of bonding molecular orbitals involves the overlap of atomic orbitals from different atoms. Sigma bonds result from the overlap along the internuclear axis, while pi bonds involve the sideways overlap.

Energy Lowering and Bond Formation

Bonding molecular orbitals contributes to the lowering of the overall energy of a molecule, making it more stable than the individual atoms. This energy lowering is a key factor in bond formation and stability.

Factors Affecting the Energy of Bonding Molecular Orbitals

The energy of the Atomic Orbitals that Combine

The energy levels of the atomic orbitals that combine to form a bonding molecular orbital influence its overall energy. Lower energy levels contribute to greater stability.

Symmetry of the Atomic Orbitals that Combine

The symmetry of the atomic orbitals affects the symmetry of the resulting bonding molecular orbitals. Symmetrical orbitals contribute to the overall stability of the molecule.

Examples of Bonding Molecular Orbitals


In the case of H₂, sigma bonding molecular orbitals are formed as a result of the overlap of two hydrogen atomic orbitals, creating a single sigma bond.

O₂ and N₂

Both oxygen (O₂) and nitrogen (N₂) molecules exhibit the formation of sigma and pi bonding molecular orbitals. These orbitals contribute to the stability and strength of the double and triple bonds present in these diatomic molecules.


Carbon monoxide (CO) showcases the interplay of sigma and pi bonding molecular orbitals, influencing its unique properties and reactivity.

Applications of Bonding Molecular Orbitals

Predicting Bond Lengths and Bond Angles

The characteristics of bonding molecular orbitals provide insights into the geometry of molecules, aiding in the prediction of bond length and angles.

Explaining Properties of Molecules

Bonding molecular orbitals contribute to the understanding of various properties, including color, magnetism, and reactivity, offering a molecular-level explanation for these phenomena.

Designing New Materials

The principles of bonding molecular orbitals find applications in materials science, enabling the design of new materials with tailored electronic and structural properties.