Question

Assertion :$N(C{H}_3{)}_3$ is pyramidal but $N(Si{H}_3{)}_3$ is planar. Reason: In $N(C{H}_3{)}_3$, lone pair on $N$ remains on it causing $lp-bp$ repulsion while in $N(Si{H}_3{)}_3$, lone pair is transferred to vacant $d$-orbital of $Si$.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

$N(C{H}_3{)}_3$ has $s{p}^3$ hybridization on nitrogen with pyramidal shape due to $p\pi -p\pi$ bonding. Whereas in $N(Si{H}_3{)}_3$ $Si$ has vacant d orbitals which provide$p\pi -d\pi$ bonding and so nitrogen has $s{p}^2$ hybridization with trigonal planar shape.

The lone pair in nitrogen remains in $N(C{H}_3{)}_3$ causing lp-bp repulsion and $N(Si{H}_3{)}_3$ lone pair is transferred to d-orbital forming $p\pi -d\pi$ bonding.

Reason is the correct explanation for assertion.