Question

What are electron deficient compounds ? Are $BC{l}_3$ and $SiC{l}_4$ electron deficient species? Explain.

Answer 1

In electron deficient compounds, the central atom either does not have eight electrons in the valence shell or it has eight electrons but can expand its valence beyond 4 due to presence of vacant d orbitals.
$BC{l}_3$ has 6 valence electrons on B atom and accepts pair of electrons from ammonia to complete its octet. Hence, it is an electron deficient compound.
In $SiC{l}_4$, the central Si atom has 8 electrons but it can expand its valency beyond 4 due to presence of vacant d orbitals. Hence, it is also an electron deficient compound.