The number of bonding electron pairs between two atoms; higher order means shorter stronger bonds.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
Bond order is the number of bonding electron pairs between two atoms. In molecular orbital theory it equals half the difference between the number of bonding and antibonding electrons. Fractional values arise in resonance structures and in ions, where electrons are shared unevenly. A higher bond order means a shorter and stronger bond, because more electron density is held between the nuclei. Bond order is one of the most useful quantities for comparing the stability of related species.
Key ideas: For Lewis structures bond order equals bonds divided by bonded positions. For MO theory use half of electrons in bonding minus electrons in antibonding. Compare isoelectronic species: N2 is 3, CO is 3, NO+ is 3, CN- is 3. Bond order of 0 means no stable bond, and removing electrons from antibonding orbitals raises it.
Common mistakes and connections: Students expect electrons to always be removed from bonding orbitals, but ionizing O2 removes an antibonding electron and strengthens the bond (O2+ is 2.5). Another error is stating that a bond order of 0.5 cannot exist, when H2+ and He2+ have it. Connects to bond length, magnetism, resonance and the MO diagrams of diatomics.
Molecular orbital bond orders across the second-row diatomics peak at 3 for N2 and fall to 0 for Ne2, which is why neon does not form a stable dimer. The interactive lesson shows this as a live animation or chart.
The bond order of the O2+ ion is 2.5, so it is stronger than neutral O2, which has a bond order of 2.
The number of bonding electron pairs between two atoms; higher order means shorter stronger bonds.
Bond Order is a intermediate topic in Bonding & Molecular Structure. It builds on the vocabulary of beginner topics in this area.
Study these earlier topics in Bonding & Molecular Structure first: Coordinate Bond, Bond Length, Bond Energy.
The next topics in Bonding & Molecular Structure are Bond Polarity and Dipole Moment.
Yes. The interactive lesson includes a self-check question on Bond Order, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Bond Order is topic 20 of 104 in Bonding & Molecular Structure.