Question

Which of the following molecules shows back bonding?

• A. $BC{l}_3$
• B. $N(Si{H}_3{)}_3$
• C. $B{F}_3$
• D. All of the above

Answer 1

The correct option is D All of the above

Back bonding occurs between the atoms in a compound in which one atom has a lone pair of electron and the other has a vacant orbital placed adjacent to each other.

$BC{l}_3$ shows back bonding when the lone pair on chlorine atom is donated to the vacant $2p$ orbital of boron.

In $N(Si{H}_3{)}_3$, the nitrogen atom has a lone pair of electrons and silicon has vacant $3d$ orbitals. Hence, back bonding occurs between the lone pair of $N$ and the empty $d-$ orbital of $Si$.
$B{F}_3$ shows back bonding when a lone pair on $F$ atom is donated to the vacant $2p$ orbital of boron.