Question

Specify the co-ordination geometry around and hybridization of $N$ and $B$ atom in a $1:1$ complex of $B{F}_3$ and $N{H}_3$ :

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

Answer 1

Answer: (A)

$N$ : tetrahedral, $s{p}^3$ ; $B$ : tetrahedral, $s{p}^3$

No doubt $N{H}_3$ and $B{F}_3$ have $s{p}^3$ (pyramidal) and $s{p}^2$ (coplanar) hybridization, respectively, having one lone pair of electron on $N$ atom which is responsible for pyramidal shape of $N{H}_3$ in spite of $s{p}^3$-hybridization. However, as soon as it is coordinated to $B{F}_3$, both attain tetrahedral geometry and acquire $s{p}^3$ hybridization.