Bond Order

Bond order is a measure of the number of bonding electron pairs between atoms. Single bonds have a bond order of 1, double bonds have a bond order of 2 and triple bonds (the maximum number) have a bond order of 3. A fractional bond order is possible in molecules and ions that have resonance structures. In the example of ozone, the bond order would be the average of a double bond and a single bond or 1.5 (3 divided by 2). As the bond order becomes larger, the bond length becomes smaller. What is the bond order of the bonds in the carbonate anion?