Molecular Orbital
Definition and meaning of Molecular Orbital in chemistry.
Molecular orbital is a mathematical function (wave function) describing the wave-like behavior of an electron within a molecule; the square of this function gives the probability of finding the electron in a given region of space. Molecular orbitals are formed by the linear combination of atomic orbitals from the constituent atoms.
In more detail
Molecular orbital theory explains bonding by treating electrons as delocalized across the entire molecule, rather than localized between specific atom pairs. When atomic orbitals overlap, they combine to form new molecular orbitals with different energies and spatial distributions. Bonding orbitals are lower in energy than the original atomic orbitals and promote stability, while antibonding orbitals are higher in energy and destabilize the molecule. Electrons fill molecular orbitals in order of increasing energy, following the Aufbau principle.
Key facts
| Abbreviation | MO |
|---|---|
| Field | Physical Chemistry |
| Formation | Linear combination of atomic orbitals (LCAO) |
| Key types | Bonding (σ, π) and antibonding (σ*, π*) |
In the hydrogen molecule (H2), the 1s atomic orbitals of each hydrogen atom combine to form a bonding molecular orbital (sigma 1s, σ1s) and an antibonding molecular orbital (sigma star 1s, σ*1s). Both electrons occupy the lower-energy bonding orbital, making H2 stable and contributing one net bond.
Frequently asked questions
How do molecular orbitals differ from atomic orbitals?
Atomic orbitals describe electron probability around a single nucleus, while molecular orbitals describe electron probability distributed across multiple atoms in a molecule.
What is the difference between bonding and antibonding orbitals?
Bonding orbitals have lower energy and increase electron density between nuclei, stabilizing the molecule. Antibonding orbitals have higher energy and decrease electron density between nuclei, destabilizing the molecule.