2. VSE
PR
1.Valence shell 2.Electron pair 3. Refulsion 4. THEORYT
= Both the bonded pairs and lone pairs of electrons determine the geometry of molecule
(2)= Electron pairs arranges themselves around the central atom to have maximum distance
and minimum repulsion
(3)= the lone pairs of electrons occupy more space than the bond pairs because lone pairs
are under the influence of only one nucleus
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3. (4)= the repulsion between electron pairs decrease in the following order
lone pairs-lone pairs >lone pairs-bond pairs > bond pairs-bond pairs
(5)= A multiple bond occupies more space than a single bond. However it is counted
as electron pairs
(6)= if all the electron pairs are bonding then the shape of molecule will be regular
(7)= the effect of bonding electron pairs decrease with increasing electronegativity of
an atom forming a molecule
(8)= the overall geometry of the molecule depends on the number of electron pairs in the
valence shell of the central atom
(9)= Deviation from the expected bond angle is due to the presence of lone pair of electron
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4. 1. shape of molecule containing two electron pairs
EXAMPLE= BeCl2
In BeCl2, there are two bonded electron in the valence shell of Beryllium. To have maximum separation. These
pairs must be at an angle of 180 to each others. This arrangement of electron pairs predict linear structure
{lewis structure} {linear or VSEPR model}
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5. EXAMPLE= BF3
Boron has three valence electron. It can be form three covalent
bond with three F-atoms. these covalent bonds pairs are situated
At the corner of an equilateral triangle, to have maximum distance
And minimum repulsion.
The F-B-F bond angle is 120 .therefore BF3 has planar triangular
Structure.
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6. EXAMPLE= SnCl2
in two bond pairs and one lone pair the structure is Angular shape and bond ang
Is 120
o
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7. Carbon has four electron in its valence shell. Carbon share these four electron with
Four electron of hydrogen atoms. Four electron pairs are present in the valence shell
Of central atom.
All these pairs are arranged in tetraheadral manner in order to have maximum
distance
The H-C-H bond angle in methane are 109.5
o
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9. Example= NH3
FOUR electron pairs are present in the valence shell of central atom of nitrogen
In NH3. three of them are bond pair and one is lone pair . According to VSEPR
THEORY lone pair –lone pair repulsion is greater then bond pair-bond pair
Repulsion .Therefore the three N-H bond pairs are pushed closer together and
The bond Angle is decrease to107.5 As a result NH3 does not show the
Expected tetraheadral arrangement but possesses a trigonal pyramidal.
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o
10. IN WATER molecule there are two bond pairs and lone pairs of electron
Around the central atom oxygen.
As lone pair- lone pair repulsion is greater than the lone pair-bond pair
Which result in the decreasing H-O-H bond angle to 104.5 the water
Molecule become V shaped as shown below.
o
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11. 1. shape of molecule containing two
electron pairs
linear
planar triangular
Angular shape With 120 angle
in tetraheadral
trigonal pyramidal
With 104.5 angle
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13. 1= THIS Theory failed because it does not explain how a chemical bond
is formed.
2= it does not explain the energetics of bonding .
3= it ignore the role pi bond in the shape of molecule
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