Question

Which one of the following does not have a pyramidal shape?

• A. $(C{H}_3{)}_{3}N$
• B. $P(C{H}_3{)}_3$
• C. $P(Si{H}_3{)}_3$
• D. $(Si{H}_3{)}_{3}N$

Answer 1

Answer: (D)

$(Si{H}_3{)}_{3}N$

$N(Si{H}_3{)}_3$ has a planar geometry due to back bonding between empty 3d orbital of Si and filled 2p orbital of N. $(C{H}_3{)}_{3}N,(Si{H}_3{)}_{3}P$ and $(C{H}_3{)}_{3}P$ have pyramidal geometry due to absence of back bonding. Nitrogen and Phosphorus are $s{p}^3$ hybridized out of which 3 hybrid orbitals are used for bond making and 1 lone pair is present in fourth orbital.