Test: VSEPR Theory, Hybridisation (May 24) - JEE MCQ

The bond pair of electrons is shared by two atoms whereas the lone pair of electrons is only under the influence of central atom.

So the electron cloud of lone pair occupies more space as compared to the bond pair.

This causes greater repulsion between the lone pairs as compared to lone pair-bond pair and bond pair-bond pair interactions.

The s-orbital is spherically symmetric in shape so it does not show preference to any direction. It is the same from all the directions.

SF₆ has an octahedral geometry.

pi-bond is always formed by sidewise overlapping of p – p orbitals in sidewise manner.

Central atom: O

At. no. = 8,

No. of valence electrons in oxygen is 6

Lewis dot structure of O atom

No. of electrons required for completing the octet = 8 - 6 =2

Atoms attached to the central atom: two H atoms

At. no. of H = 1

H atoms need one electron each for getting fully-filled K shells.

Representation of Lewis dot structures of H2O, which satisfies these conditions:

No. of valence shell electron pairs on the central atom O, after forming two covalent bonds with two H atoms = 4.

Geometry of 4 pairs, as predicted by VSEPR theory = Tetrahedral.

No. of lone pairs = Two.

Type, according to VSEPR theory:

So, geometry of pairs and geometry of atoms are different.

The geometry of atoms is derived from the geometry of pairs. At two of the four corners of the tetrahedron, there are no atoms.

Diagrams showing the geometry of 2 H atoms and two lone pairs:

Geometry of atoms in H2O is V-shaped. i.e. H2O molecule has a bent geometry

(b) BrF₃ - T-shaped (sp³d²)

Has no lone pair thus, bond angle is 120°. B-atom is sp²-hybridised.

Central atom E is sp³-hybridised. Hence, angle < 120°. As we go down the group, (Ip-bp) repulsion decreases. Hence, angle 
(Cl—E—Cl) PCI₃ > AsCI₃ > BiCI₃.
Thus, order is BCI₃ > PCI₃ > AsCI₃ > BiCI₃.

 sp³d -hybridised Cl-atom - (T-shaped s tructure)
  sp³ -hybridised. Cl-atom (Bent)
 sp³d -hybridised As-atom (Trigonal bipyramidai).
 sp³d² -hybridised As-atom (Octahedral).