sblock Elements 1 Question 14
10. The hydride that is not electron deficient is
(2019 Main, 11 Jan II)
(a) $\mathrm{AlH} _{3}$
(b) $\mathrm{B} _{2} \mathrm{H} _{6}$
(c) $\mathrm{SiH} _{4}$
(d) $\mathrm{GaH} _{3}$
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Answer:
Correct Answer: 10. (c)
Solution:
- $\mathrm{GaH} _{3}, \mathrm{AlH} _{3}$ and $\mathrm{B} _{2} \mathrm{H} _{6}$ are the hydrides of group-13 $\left(n s^{2} n p^{1}\right)$, whereas $\mathrm{SiH} _{4}$ is an hydride of group 14.
So, $\mathrm{B} _{2} \mathrm{H} _{6}, \mathrm{AlH} _{3}$ and $\mathrm{GaH} _{3}$ are electron deficient hydrides. But, $\mathrm{SiH} _{4}$ is an electron precise hydride of group-14 $\left(n s^{2} n p^{2}\right)$, i.e. these hydrides can have the required number of electrons to write their conventional Lewis structures.
