Question

What is the geometry of nitrogen atom in $N{H}_3,N{\left(C{H}_3\right)}_3$ and $N{\left[Si{\left(C{H}_3\right)}_3\right]}_3$ ?
I. Trigonal planar
II. Trigonal pyramidal
III. Square planar

• A. I, I, I
• B. II, II, III
• C. II, I, II
• D. II, II, I

Answer 1

Answer: (D)

$N{H}_3$ Trigonal pyramidal due to
$N{\left(C{H}_3\right)}_3$ $ip-bp$ repulsion (instead of tetrahedral
In $N{\left[{\left(Si{\left(C{H}_3\right)}_3\right)}_3\right]}_3$ structure is triangular planar as lone pair on $N$-atom is transferred to the empty $d$-orbitals of silicon ( $p\pi -d\pi$ overlapping and its Lewis base character is lost. Thus, II, II, I