Question

The species which is Pyramind in shape ? (a)SO3 (b) BrF3 (c) SiO3 ^2- (d) OSF2

Answer 1

SO3 ⇒ 3 bond pairs ⇒ sp2 hybrid ⇒ trigonal planar
BrF3 ⇒ 3 bond pairs, 2 lone pairs ⇒ sp3d hybrid ⇒ T-shaped
(SiO3)2- ⇒ 3 bond pairs ⇒ sp2 ⇒ trig. plan.
OSF2 ⇒ 3 b.p., 1 l.p. ⇒ sp3 hybrid ⇒ pyramidal.

Answer 2

Answer: $OSF_2$

Explanation:

Formula used

$:{\text{Number of electrons}} =\frac{1}{2}[V+N-C+A]$

where, V = number of valence electrons present in central atom

N = number of monovalent atoms bonded to central atom

C = charge of cation

A = charge of anion

1. $SO_3$

${\text{Number of electrons}} =\frac{1}{2}[6]=3$

The number of electron pairs is 3 that means the hybridization will be $sp^2$ and the electronic geometry of the molecule will be trigonal planar.

2. $BrF_3$

${\text{Number of electrons}} =\frac{1}{2}[7+3]=5$

The number of electron pairs is 5 that means the hybridization will be $sp^3d$ and the electronic geometry of the molecule will be trigonal bipyramidal.

But as there are three atoms around the central carbon, the fourth and position will be occupied by lone pair of electrons. The repulsion between lone and bond pair of electrons is more and hence the molecular geometry will be T shaped.

3. $SiO_3^{2-}$

${\text{Number of electrons}} =\frac{1}{2}[4+2]=3$

The number of electron pairs is 4 that means the hybridization will be $sp^2$ and the electronic geometry of the molecule will be trigonal planar.

4. $OSF_2$

${\text{Number of electrons}} =\frac{1}{2}[6+2]=4$

The number of electron pairs is 4 that means the hybridization will be $sp^3$ and the electronic geometry of the molecule will be tetrahedral.

But as there are three atoms around the central carbon, the fourth position will be occupied by lone pair of electrons. The repulsion between lone and bond pair of electrons is more and hence the molecular geometry will be pyramidal.