pBlock ElementsII 1 Question 1
1. The correct statement among the following is
(2019 Main, 12 April I)
(a) $\left(\mathrm{SiH} _{3}\right) _{3} \mathrm{N}$ is planar and less basic than $\left(\mathrm{CH} _{3}\right) _{3} \mathrm{N}$.
(b) $\left(\mathrm{SiH} _{3}\right) _{3} \mathrm{N}$ is pyramidal and more basic than $\left(\mathrm{CH} _{3}\right) _{3} \mathrm{N}$.
(c) $\left(\mathrm{SiH} _{3}\right) _{3} \mathrm{N}$ is pyramidal and less basic than $\left(\mathrm{CH} _{3}\right) _{3} \mathrm{N}$.
(d) $(\mathrm{SiH} _{3}) _{3} \mathrm{N}$ is pyramidal and less basic than $(\mathrm{CH} _{3}) _{3} \mathrm{N}$.
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Answer:
Correct Answer: 1. (a)
Solution:
- The correct statement is that $\left(\mathrm{SiH} _{3}\right) _{3} \mathrm{N}$ is planar and less basic than $\left(\mathrm{CH} _{3}\right) _{3} \mathrm{N}$. The compounds trimethylamine $\left(\mathrm{CH} _{3}\right) _{3} \mathrm{N}$ and trisilylamine $\left(\mathrm{SiH} _{3}\right) _{3} \mathrm{N}$ have similar formulae, but have totally different structures. In trimethylamine the arrangement of electrons is as follows :
In trisilylamine, three $s p^{3}$ orbitals are used for $\sigma$-bonding, giving a trigonal planar structure.
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