A lower-energy combination of atomic orbitals that concentrates electron density between nuclei.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
A bonding molecular orbital results from constructive, in-phase overlap of atomic orbitals, which concentrates electron density between the nuclei. Because the nuclei are attracted to this shared density, the energy of a bonding orbital is lower than that of the original atomic orbitals. Electrons placed in bonding orbitals stabilize the molecule and contribute to its bond order. Bonding orbitals are labelled sigma or pi according to their symmetry about the bond axis, and sigma bonding orbitals are cylindrically symmetric. The lower the energy of a bonding orbital, the more strongly it holds the bonded atoms together.
Key ideas: Recognize them by no node between the nuclei and electron density piled up in the bonding region. A sigma bonding orbital has no nodal plane containing the axis, and a pi bonding orbital has one along the internuclear axis. Each orbital holds up to two electrons of opposite spin. The energy lowering is the source of the bond energy.
Common mistakes and connections: Students think a bonding orbital must lie between the atoms as a physical region, but it is a wavefunction extending to the whole molecule. Another error is expecting electrons in a bonding orbital to belong to one atom. Remember: a bonding MO is not necessarily lower than all atomic orbitals if mixing is strong. Links to antibonding MOs, bond order and spectroscopy.
In-phase addition of two 1s orbitals builds up amplitude between the nuclei, increasing electron density where it stabilizes the bond. The interactive lesson shows this as a live animation or chart.
Combining two 1s orbitals in H2 gives a sigma 1s bonding orbital that holds both electrons.
A lower-energy combination of atomic orbitals that concentrates electron density between nuclei.
Bonding Molecular Orbital is a advanced topic in Bonding & Molecular Structure. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Bonding & Molecular Structure first: sp3d and sp3d2 Hybridization, Hybridization of Water and Ammonia, Molecular Orbital Theory.
The next topics in Bonding & Molecular Structure are Antibonding Molecular Orbital and MO Diagram of Homonuclear Diatomics.
Yes. The interactive lesson includes a self-check question on Bonding Molecular Orbital, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Bonding Molecular Orbital is topic 60 of 104 in Bonding & Molecular Structure.