Chemical Bonding and Molecular Structure

VSEPR Theory and Geometry of Molecules

VSEPR Theory :
The valency shell is assumed as a sphere and the electron pairs are arranged around the central atom.
A multiple bond is treated as single super electron pair.
Repulsion lp – lp > lp – bp > bp – bp
ex ; sp2 type → No. of Bp's → 2, Lp's → 1
                        Geometry → Trigonal planar
                             Shape → Angular
Ex : SnCl2, HgCl2

 Hybridization No. of Bp's No. of Lp's Geometry Shape Example
sp3 4 - Tetrahedron Tetrahedron CH_{4}, CCl_{4},SO_4^{-2},NH_4^+
sp3 3 1 Tetrahedron Pyramid NH_{3}, NCl_{3},PH_{3},SO_3^{-2}
sp3 2 2 Tetrahedron V- Shape, bent shape H_{2}O, OF_{2},Cl_{2}O


 Hybridization No. Bp's No. of Lp's Geometry Shape Example
sp3d 5 0 Trigonal bipyramidal Trigonal bipyramidal PF_{5}, PCl_{5}
sp3d 4 1 Trigonal bipyramidal see saw SF_{4}, SCl_{4}
sp3d 3 2 Trigonal bipyramidal T - shape BrF_{3}, RCl_{3},ClF_{3}
sp3d 2 3 Trigonal bipyramidal Linear I_3^-,XeF_{2},ICl_2^{-}
sp3d3 7 0 Pentagonal bipyramidal Pentagonal bipyramidal IF_{7}
sp3d3 6 1 Pentagonal bipyramidall Distorted octahedron XeF_{6}

 Short cut hybridization formula :

Formal charge :
F.C = valence electrons − (no. of lone pair electrons + no. of bond pairs)

1) Oxygen atom
     6 − (2 + 3)
     6 − 5 = 1
2) 2nd oxygen
    6 − (4 + 2) = 0
3) 3rd oxygen
    6 − (6 + 1) = 6 − 7 = −1

Part1: View the Topic in this Video from 0:49 to 56:39

Part2: View the Topic in this Video from 0:40 to 4:52

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