CHEMISTRY COMMUNITY

I understand that Bond Order represents the number of bonds between two atoms, which makes sense with integer numbers. But how do you make sense of a bond order like 1.5 for example. Can there be half of a bond? How does this work with a diatomic arrangement?

A bond order of 1.5 would mean that there are resonance structures, as a resonance hybrid would result from the blending of two or more possible Lewis structures for the molecule or ion. The average of the bonds in each structure could result in a number like 1.5. In addition, bond order can also tell you how strong a bond is, as a bond order of 1 (a single bond) is weaker than that of 2 (a double bond). Likewise, a molecule with a bond order of 1.5 has a stronger bond than a molecule with a bond order of 1 does.

A bond order of 1.5 signifies that the Lewis structure of the compound has resonance structures, and that the bonds of the compound will have the characteristics of both a single and double bond.

The resonance structures don't truly tell us how the bonds are in reality, so a bond order of 1.5 helps us make sense of the fact that the bonds will be like a combo of a single and double bond.

Because there are only two atoms in a diatomic molecule there cannot be resonance. A fractional bond order such as 1.5 indicates that the molecule in question is less stable than another with a higher bond order like 2. However, it would still be more stable than a molecule with a BO of 1, which has less attraction between its atoms.