Answer to Question #75279 in Inorganic Chemistry for Arun Rawat

Question

a) In carbonate ion, all the three CO bonds have identical bond length. Explain.

Answer 1

In Carbonate ions, the 4 p-orbitals of the 4 atoms overlap. This basically means that all 4 p-orbitals of the double-bonds sort of join together at the central atom in this case, the Carbon atom.
Two of the three Oxygen atoms in the Carbonate ion has an extra electron which makes its overall charge -2. When electrons linger at atoms which don’t compensate for its charge, they’d rather form a bond with another electron from another atom essentially staying in between the atoms so that its charge would be spread between the two. When these two electrons pair up in the centre of the Carbon and Oxygen atoms, their orbitals, one of the p-orbitals, overlap, thus forming a pi-bond.
However, there is another Oxygen atom that wants to do the same. Yet, Carbon can only have 4 bonds around it. That is including the other single-bonded oxygen. Both of these single bonded Oxygens have a charge of -1 due to the excess electron thus both would strive to get a spot in Carbon’s p-orbital.
Therefore, we can now say that at any given time, there is going to be a double-bonded Oxygen and 2 single bonded, negatively charged Oxygens. However, again, two of these Oxygens will fight to get that double bond. Thus, by mere random chance, one of the two Oxygens will get to get it with the Carbon at the same time knocking out the electron of the pi-bond of the previously double bonded Oxygen and returning it to it.
The location of the double bond has now changed. But the same thing will soon happen again, very, very quickly, millions of times a second to the extent that the changing of the bonds is practically undetectable.
The bond lengths are the same because of this continuous position shift in the double bond. They do change a bit but the shift in the position of the double bond is very quick that they practically seem constant and seem to be everywhere.