Antibonding Orbital
Definition and meaning of Antibonding Orbital in chemistry.
An antibonding orbital is a molecular orbital formed by destructive interference of atomic orbitals, characterized by a nodal plane between the nuclei and higher energy than the parent atomic orbitals. Electrons occupying antibonding orbitals reduce overall bond strength and stability.
In more detail
When two atomic orbitals combine, they create both bonding (constructive interference) and antibonding (destructive interference) molecular orbitals. Antibonding orbitals feature a nodal plane perpendicular to the internuclear axis, concentrating electron density away from the bonding region. This distribution actively weakens the chemical bond. Antibonding orbitals are denoted with an asterisk (σ*, π*) and are essential to molecular orbital theory for predicting molecular stability and reactivity patterns.
Key facts
| Notation | Denoted with asterisk: σ*, π* |
|---|---|
| Formation | Results from destructive interference of atomic orbitals |
| Effect on bonding | Reduces bond stability when occupied |
| Field | Physical Chemistry |
In hydrogen (H2), the 1s atomic orbitals combine to form σ and σ* molecular orbitals; the σ* orbital remains unoccupied in ground-state H2 but can be populated through photon absorption or in molecules with sufficient valence electrons.
Frequently asked questions
How do antibonding orbitals differ from bonding orbitals?
Antibonding orbitals have a nodal plane between nuclei and higher energy, while bonding orbitals concentrate electron density between nuclei with lower energy. Electrons in antibonding orbitals destabilize bonds; those in bonding orbitals stabilize them.
When are antibonding orbitals occupied?
Antibonding orbitals remain empty in ground-state molecules but become populated in excited states or in molecules with many valence electrons where all lower-energy orbitals are filled.