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Bond Order

Bond order = (N_bonding − N_antibonding) / 2
Quick Reference
Formula / NotationBond order = (N_bonding − N_antibonding) / 2
Also Known AsMultiplicity (bond), MO bond order, bond multiplicity

What is Bond Order?

Bond order is the number of shared electron pairs between two bonded atoms, or more precisely, half the difference between the number of bonding and antibonding electrons in molecular orbital theory. A bond order of 1 indicates a single bond, 2 a double bond, and 3 a triple bond. Higher bond order correlates with shorter bond length and greater bond energy.

Formula & Notation

Bond order = (N_bonding − N_antibonding) / 2

Other Names / Synonyms: Multiplicity (bond), MO bond order, bond multiplicity

Properties & Characteristics

Bond order is a measure of the number of chemical bonds between two atoms in a molecule or ion. In simple terms: single bond = 1, double bond = 2, triple bond = 3. In molecular orbital theory, bond order = (bonding electrons − antibonding electrons)/2. Fractional bond orders are possible (e.g., O₂ bond order = 2; NO bond order = 1.5; H₂⁺ bond order = 0.5). Higher bond order correlates with shorter bond length and greater bond energy.

Uses & Applications

Bond order is used to predict molecular stability, magnetic properties (paramagnetic if unpaired electrons in MOs), spectroscopic behaviour, and reactivity. It rationalises why N₂ (bond order 3) is very unreactive and why O₂ (bond order 2) is paramagnetic.

Safety Information

Molecules with high bond order (e.g., triple bonds) in strained rings or reactive intermediates can be energetic. Understanding bond order helps predict explosive decomposition pathways and the stability of reactive species in hazardous reactions.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Bond Order
Formula Bond order = (N_bonding − N_antibonding) / 2
Synonyms Multiplicity (bond), MO bond order, bond multiplicity

Frequently Asked Questions

Bond order is the number of shared electron pairs between two bonded atoms, or more precisely, half the difference between the number of bonding and antibonding electrons in molecular orbital theory. A bond order of 1 indicates a single bond, 2 a double bond, and 3 a triple bond. Higher bond order correlates with shorter bond length and greater bond energy.

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