Although boric acid `B(OH)_(3)`, contains three hydroxyl groups yet it behaves as a monobasic acid. Explain why?

Explanation

Because of the small size of boron atom and presence of only six electron in its valence shell in `B(OH)_(3)` it coordinates with the oxygen atom of the `H_(2)O` molecules of form a hydrated species.

In this hydrated species `B^(3+)` ion because of its small size it has a high polarizing power and hence pulls the electron of the coordinated oxygen atom towards it. the coordinate O-atom, in turn pulls the O-electron of thhe O-H bond, there by facilitating the release of a proton. As a result, `B(OH)_(3)` acts as a weak monobasic lewis acid and thus reacts with NaOH solution to form sodium metaborate.