Question

The states of hybridization of boron and oxygen atoms in boric acid (H3BO3) are respectively :

• A. sp2 and sp2
• B. sp2 and sp3
• C. sp3 and sp2
• D. sp3 and sp3

Answer 1

Answer: (A)

sp2 and sp2

Answer 2

For planar BO3 groups, the B–O bond length is usually close to 1.36 Å but for tetrahedral BO4 groups the length increases to about 1.48 Å. This suggests that in the planar grouping $\pi$ -boding involving lone pairs of electrons from the oxygen atoms occurs; this $\pi$ -boding is necessarily lost in the tetrahedral group, in which a lone pair from the extra oxygen atom occupies the previously empty orbital on the boron atom.