Question

Trimethylammonia is pyramidal whereas trisilylammonia is a planar molecule. Why?

• A. In silicon atom, the electron pair of nitrogen is involved in $\mathrm { p } \pi - \mathrm { d } \pi$ bonding
• B. In nitrogen, lone pair of electrons is present at nitrogen hence it has pyramidal shape.
• C. Both (1) and (2) are correct.
• D. Both (1)and (2) are wrong.

Answer 1

Answer: (C)

Both (1) and (2) are correct.

Answer 2

: In silicon atom, there is a vacant d – orbital hence electron pair of nitrogen is donated to silicon by $\mathrm { p } \pi - \mathrm { d } \pi$ bonding in trisilylammonia. Hence it has a planar structure. In trimethyl ammonia, the shape is pyramidal due to presence of lone pair of electrons at nitrogen.