# Bond order of HCO3- as compared to (CO3)2-

How can we say that the bond order of $\ce{HCO3-}$ is less than that of $\ce{CO3^2-}$? I see that the resonance in $\ce{HCO3-}$ is not as effective as in latter because in latter it is equi-energy resonating structures, and thus energy released in $\ce{HCO3-}$ would be less. But how does that relate to the bond order? The bond order of $\ce{CO3^2-}$ should be $\ce{4/3}$, but why can we say that $\ce{HCO3-}$ will be slightly less than $\ce{4/3}$?

• Can we really?$%$ – Jan Dec 7 '15 at 14:05
• See previous post chemistry.stackexchange.com/questions/1302/… – iad22agp Dec 7 '15 at 21:23
• Yes but then can we talk about BO or Bond length of HCO3-? – Shodai Dec 8 '15 at 9:11
• You can view bicarbonate approximately as hydroxyl + carboxylate, with bond orders appropriate for them. – Mithoron Dec 8 '15 at 16:34