Note that the bond order equation can also yield a fractional bond order, which has not been possible with other theories. Any bond order greater than zero, fractional or not, reflects a stable molecule.
Consider three proposed species of hydrogen: an H2– ion, an H2 molecule, and an H2+ ion. Calculating the bond order can predict whether these species are stable. First, look at the H2– ion. This structure has three electrons. The first two electrons enter the lower-energy bonding orbital, and the last electron enters the antibonding orbital. The bond order is therefore . Because 0.5 is greater than zero, this molecule is stable and has a "half" bond.
Next, consider the H2 molecule. H2 has two electrons, both in the bonding orbital with no antibonding electrons. The bond order is . The bond order indicates a stable single bond.Finally, consider H2+. This molecule has one electron in the bonding orbital and no antibonding electrons. The bond order is . So, like the first ion, H2+ is stable with a "half" bond. The bond order of the H2 molecule is 1, and the bond orders of the H2– ion and the H2+ ion are 0.5. The H2 molecule has the highest bonding order and is the most stable of these species.