Question

Which of the following is the correct prediction about observed $B-F$ bond length, in $B{F}_3$ molecule?

• A. The bond length is more than actual because of the large difference in electronegativity value.
• B. The small bond length is due to $p\pi -p\pi$ back bonding.
• C. Both $\left(a\right)$ and $\left(b\right)$
• D. None of these

Answer 1

The correct option is B The small bond length is due to $p\pi -p\pi$ back bonding.

In boron trifluoride, $B{F}_3$, backbonding is possible as a lone pair of electrons from $F$ atom flow into the vacant $p$ orbital of the electron-deficient $B$ atom.

As a back bond is a partial double bond so bond length decreases due to back bonding.