Question

Specify the coordination geometry and hybridisation of $N$ and $B$ atoms in a $1 : 1$ complex of $BF _{3}$ and $NH _{3}$

• A. $N :$ tetrahedral, $s p^{3} ; B :$ tetrahedral, $s p^{3}$
• B. $N :$ pyramidal, $s p^{3} ; B :$ pyramidal, $s p^{3}$
• C. $N$ : pyramidal, $s p^{3} ; B :$ planar, $s p^{2}$
• D. $N :$ pyramidal, $s p^{3} ; B :$ tetrahedral $, s p^{3}$

Answer 1

Answer: (A)

$NH _{3}$ and $BF _{3}$ have $s p^{3}$ (pyramidal) and $s p^{2}$ (planar) hybridisation respectively having one lone pair of electron on $N$ atom which is responsible for pyramidal shape of $NH _{3}$ inspite of $s p^{3}$ hybridization. However, as soon as it is coordinated to $BF _{3}$, both attain tetrahedral geometry and acquire $s p^{3}$ hybridisation.