IB Chemistry on VSEPR

1. brown liquid
Click here simulation on covalent bond
yellow gas
greenish gas
violet solid
Covalent bonding between non metals
2.8.7
Gp 17 Non metal
achieve stable octet structure
CI shared pair electron
Covalent Bonding
Electrostatic forces attraction between
nucleus with shared pair electron
2.8.8
2.8.7
Sharing
electron
Gp 17 Non metal
2.8.8
CI
Non metal
• High EN value
• Gain electron (anion)
• Electronegative ions
Covalent Bond Group 17
CICI
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
CI CI: x
x
::
:.
x
x
X
x
x
x
x CI CI
::
x
x
x
x
CI CI
Non metal
• High EN value
• Gain electron (anion)
• Electronegative ions
Single covalent bond – shared pair electron

2. Covalent bonding between non metals
Covalent Bonding
Single covalent bond
ONE pair shared e
2.8.8 2.8.8
Covalent Bond
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
CI CI:
x
x
::
:
:
.
x
x
X
X
x
x
x
x
x
x
O
CI CI::
x
x
x
x
x
x
CI CI
Sharing
electron
Bond Strength
2.8 2.8
Sharing
electron
O O: x
x O
N
O O
N:
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
C
: :. N N: N N
:
Covalent Bonding
Double covalent bond
TWO pair shared e
Covalent Bonding
Triple covalent bond
THREE pair shared e
O
x
x: CO CO O O O
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
Covalent Bonding
Double covalent bond
TWO pair shared e

3. :
.
CI
..
x
Bond Bond
order
Bond
strength
Bond
length/pm
C - C 1 347 154
C = C 2 612 134
C Ξ C 3 820 120
N - N 1 159 145
N = N 2 418 123
N Ξ N 3 914 110
Bond length and Bond strength
Bond length = 0.199nm
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
CI CI:
x
x
::
:
:
.
x
x
X
X
x
x
x
x
O
CI CI::
x
x
x
x
x
x
CI CI
O O: x
x O
N
O O
N:
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
Lewis structure/diagram
. Electron cross dot
. Valence/bonding pair electron
O
: :
.
N N: N N
:
Triple bond > Double bond > Single bond
Bonding pair e
-involve in bonding
Bond length decrease
Bond strength Increase
(Double/Triple bond)
Bond length = 0.121nm
Bond length = 0.110nm
Bond order up – Bond strength up – Bond length down
O:
Non bonding pair
(Lone pair electron)
Bonding
pair electron
C O: :
Bonding pair electron
Dative bond
(electron pair of oxy)
Types of bonding
Lone pair e
–not involve in bonding
Dative/coordinate bond
- pair e come from an atom
Exception to octet rule
All period 2 element
- observe octet rule
except Be and B
Electron deficient
Less than 8 valence e
Expanded octet
More than 8 valence e
All period 3 element
- observe octet rule
except P and S
: BeCI CIx
. :
::
::
x
x.
Be - 4 valence e
BCI CI
:
::
:
:: x
: :B - 6 valence e
P S
CI
CI
CI
CI
CI
CI
CICI
CICI
CI
P - 10 valence e
S – 12 valence e

4. Valence Shell Electron Pair Repulsion
Predict molecular shape/geometry Shape determine by electron pairs/
electron charge centers/ECC
Bonding/lone pair – repel each other
Bonding/lone pair arrange themselves as far as possible
(minimise repulsion)
Valence
Shell
Electron
Pair
Repulsion
NOT surrounding atoms
N
H
HH
..
Principles of VSEPR
Shape of molecule
Determine number valence e around central atom1
2 Single, double, triple bond , lone pair act as electron
charge center/ECC
3
4 Lone pair-lone pair > Lone pair-bonding pair > bonding pair-
bonding pair repulsion
5
6 ECC or electron pair position in equatorial first, then axial
Excellent VSEPR simulation Click here ✓ Click here VSEPR notes
Lewis structure
VSEPR
..
N
H
H
H
Shape
Click here VSEPR simulation

5. Valence Shell Electron Pair Repulsion
Bonding/lone pair arrange themselves as far as possible
(minimise repulsion)
Principles of VSEPR
Determine number valence e around central atom1
2 Single, double, triple bond , lone pair act as
electron charge center/ECC
3 Bonding/lone pair repel each other
Lone /lone pair > Lone /bond pair > bond/bond pair repulsion
4
5
For 5/6 ECC:
ECC position in equatorial first, then axial
..
N
HHH
3 bonding pair
1 lone pair
4 ECC
N – central atom
3 ECC
C
H
=O
H
H C N
2 ECC
OH H
4 ECC
> >
1 lone pair2 lone pair 0 lone pair
Repulsion greater - Bond angle smaller
Repulsion
greater
Repulsion
greater
✓
ECC far apart – Bond angle greatest – minimise repulsion
6
Lone pair need more space
Multiple bonds more space
Unequal repulsionEqual repulsion
90°
120°
109.5°
107°
180°

6. H
Bond angle - 104.5°
Linear
Bond angle - 180°
O
OO C BeH N
B
 X
 x
C SO
O C H NO
C OO CH N HH Be N OX
x
 X
X 
X 
X 
X
X
 X
 x
X
x
+
+
:
F
F
F
H
H O O
O
C
O
O
O
B X
F
F
F
C
H
H
x
x
O S
O O
C
O
x
x
O
2-
2-
O
x
x
:
||
BF3 CH2 O SO3 CO3
2-
CO2 HCN BeH2 NO2
+Lone
Pair
Bonding
Pair
Geometry 2 bond pair
✓
= =
Geometry
3 bond pair
Bond angle - 120°
Trigonal
planar
✓
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R
O3
O
O O
:
O
O
:
O
NO2

N
OO

N
OO
NO2
-
N
OO
:
N
OO
:
SO2
OO
-
-
S
:
S
OO :
Geometry
2 bond pair
1 lone pair
Bent ✓
E
L
E
C
T
R
O
N
C
E
N
T
E
R

7. Bond angle -109.5°
Bond angle -104.5°
O
Bond angle- 107°
Tetrahedral
Trigonal
Pyrimidal
N
H
N
:
:
O
SO3
2-PH3NH3
O
HH
H2O
H H
O
O
F2O
F F
F F
O
S
CICI
SCI2
N
H H
S
CI CI
N
H
NH2
-
-
-
H: : : : :
:
:
:
:
: : Bent
CIO3
-
H
H
P
H
H
H
H
H
H
P
H
H
H
:
O
O
S
O
S
O
:
O
2-
2-
CI
O
O
O
CI
:
O
O
-
:
CH4
C
H
NH4
+ BH4
- PCI4
+
H
H
H
H
C
H
H
H

N
H
H H
H
H
N
H
H
H

H
B
HH H
H
B
H

H
H
CI
CI CI CI
P
CI
CI
CI
P

CI
-
-
+
+
+
+
::
:
::
::
: :
::
:
:
:
:
:
Lone
Pair
Bonding
Pair
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R
Geometry
2 bond pair
2 lone pair
Geometry
3 bond pair
1 lone pair
✓
Geometry
4 bond pair
✓
-
✓

8. :
:
:
:
:
:
Linear
Bond angle 180°
Bond angle <90°
T shape
Bond angle <90° , <120°
Trigonal
Bipyrimidal
Bond angle - 90° , 120°
P CI
CI
CI
CI
CI
:
P

CI
 CI
CI
CI


S
F
F
F
F
S
F


F
F
F
Te
CI
CI
CI
CI
Te
CI
CI
CI
CI
:
CI
F
F
F
CI
F

F
F

I
CI
CI
CI
CI
I


CI

CI
I
F
F
F
F
F
I

F
F

F
Xe
F
F
O
O
Xe

F

F
O
O
:
+
+
:
CI
I
I
I
Xe
CI
CI
I
F
F
:::::::
:
:
::
::
::
:
:
:
:
:
::
:
:
::
:
:
:
:
:
::
::
:
::::
:
:
::
:
::
:
::
::
:
::
:
::
:
::
:
::
::
::
::
::
::
:
BrF
F
F
Br
F



F
F
: :
:
: :
:
::
:
-
PCI5
SF4
TeCI4 (IF4)+ XeO2F2
CIF3 ICI3 BrF3
(I3)-
(ICI2)- XeF2
-
Bonding
Pair
Lone
Pair
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R
: : : :
Geometry 5 bond pair
✓
Geometry
4 bond pair
1 lone pair
Seesaw ✓
Geometry
3 bond pair
2 lone pair
✓
2 bond pair
3 lone pair
(XeF3 )+
F
F Xe
F
F
Xe
 F
F
::
:
::
::
::
+
+
✓
Geometry

9. Linear
Square
planar
F
S
SF6
F
F
F
F
F
PCI6
-
P
CI
CI
CI
CI
CI
CI
IF5O
I
O
||
F
F
F
F
F
F

S
F

F
F
F
F
CI
P
CI


CI
CI
CI
CI
I
F
F
F

F
F
::
O
Square
pyrimidal

CI
Sb
Sb
CI
CI
CICI
CI
CI
CICI
CI
(SbCI5)2- BrF5
Xe
F
FF
F
Xe
XeF4
F
F
F
Br
F
FF
F
F
Br
 F
F
O
F
F
Xe
||
F
FF
F
O
::
Xe
F
F
F
F
F
Te
F
FF
F
F

Te
F
F
F
F
XeOF4 (TeF5)-
-
-
CICI
I
CICI
(ICI4)- -
:
:
:
:
:
:
::
:
:
:
::
:::
:
::
:
::::
::
:
:
:
:
:
:
:
::
:
:
:
:
::
: :::
:
:
:
:
::
:
::
:
::::
:
::::
::::
:
:
:
::
::
:
:
:
:
:
::::
::::
:
:
:::
::::
:
::
:
:
:
:
:
:
::
:::
::::
:
2-
2-
:
-
-
Lone
Pair
Bonding
Pair
::
::
:
::::
::::
:
: :
:
:
:
:
:
:
:
::
::
:
(XeF3) -
F
(XeF2)2-
F
F
Xe
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R Lone pair in equatorial first, then axial
Lone pair in equatorial first, then axial
:
:
:
:
-
2-
Minimise repulsion
Minimise repulsion
Geometry 6 bond pair
Bond angle - 90°
Octahedral ✓
Geometry
5 bond pair
1 lone pair
Bond angle < 90°
✓
4 bond pair
2 lone pair
Bond angle - 90°
✓
3 bond pair
3 lone pair
Bond angle - <90°
T shape ✓
2 bond pair
4 lone pair
Bond angle - 180°
✓

10. H
Bond angle
104.5°
Linear
Bond angle
180°
O
OO C BeH N
B
 X
 x
C SO
O C H NO
C OO CH N HH Be N OX
x
 X
X 
X 
X 
X
X
 X
 x
X
x
+
+
:
F
F
F
H
H O O
O
C
O
O
O
B X
F
F
F
C
H
H
x
x
O S
O O
C
O
x
x
O
2-
2-
O
x
x
:
||
BF3 CH2 O SO3 CO3
2-
CO2 HCN BeH2 NO2
+Lone
Pair
Bonding
Pair
ECC = 2
2 bond pair
✓
= =
ECC = 3
3 bond pair
Bond angle
120° Trigonal
planar
✓
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R
O3
O
O O
:
O
O
:
O
NO2

N
OO

N
OO
NO2
-
N
OO
:
N
OO
:
SO2
OO
-
-
S
:
S
OO :
ECC = 3
2 bond pair
1 lone pair
Bent ✓
E
L
E
C
T
R
O
N
C
E
N
T
E
R
Equal repulsion
Electron
Distribution
(LINEAR)
Equal repulsion
Electron
Distribution
(TRIGONAL PLANAR)
Unequal repulsion
Electron
Distribution
(TRIGONAL PLANAR)

11. Bond angle
109.5°
Bond angle
104.5°
O
Bond angle
107°
Tetrahedral
Trigonal
Pyrimidal
N
H
N
:
:
O
SO3
2-PH3NH3
O
HH
H2O
H H
O
O
F2O
F F
F F
O
S
CICI
SCI2
N
H H
S
CI CI
N
H
NH2
-
-
-
H: : : : :
:
:
:
:
: :
Bent
CIO3
-
H
H
P
H
H
H
H
H
H
P
H
H
H
:
O
O
S
O
S
O
:
O
2-
2-
CI
O
O
O
CI
:
O
O
-
:
CH4
C
H
NH4
+ BH4
- PCI4
+
H
H
H
H
C
H
H
H

N
H
H H
H
H
N
H
H
H

H
B
HH H
H
B
H

H
H
CI
CI CI CI
P
CI
CI
CI
P

CI
-
-
+
+
+
+
::
:
::
::
: :
::
:
:
:
:
:
Lone
Pair
Bonding
Pair
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R
2 bond pair
2 lone pair
ECC = 4
3 bond pair
1 lone pair
✓
ECC = 4
4 bond pair
✓
-
✓
ECC = 4
Electron
Distribution
(TETRAHEDRAL)
Unequal repulsion
Unequal repulsion
Electron
Distribution
(TETRAHEDRAL)
Equal repulsion
Electron
Distribution
(TETRAHEDRAL)

12. Bond angle
180° Linear
Bond angle
<90°
T shape
Bond angle
< 90° , < 120°
Trigonal
BipyrimidalBond angle
90° , 120°
P CI
CI
CI
CI
CI
:
P

CI
 CI
CI
CI


S
F
F
F
F
S
F


F
F
F
Te
CI
CI
CI
CI
Te
CI
CI
CI
CI
:
CI
F
F
F
CI
F

F
F

I
CI
CI
CI
CI
I


CI

CI
I
F
F
F
F
F
I

F
F

F
Xe
F
F
O
O
Xe

F

F
O
O
:
+
+
:
CI


I
I
I


Xe
CI
CI
I

F
F

:::::::
:
:
::
::
::
:
:
:
:
:
::
:
:
::
:
:
:
:
:
::
::
:
::::
:
:
::
:
::
:
::
::
:
::
:
::
:
::
::
::
::
::
::
::
::
::
:
: : :
BrF
F
F
Br
F



F
F
: :
:
: :
:
::
:
-
PCI5
SF4
TeCI4 (IF4)+ XeO2F2
CIF3 ICI3 BrF3
(I3)-
(ICI2)- XeF2
-
Bonding
Pair
Lone
Pair
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R
: : : :
ECC = 5
5 bond pair
✓
ECC = 5
4 bond pair
1 lone pair
Seesaw ✓
ECC = 5
3 bond pair
2 lone pair
✓
ECC = 5
2 bond pair
3 lone pair
F
F Xe
F
F
Xe
 F
F
::
:
::
::
::
+
+
✓
Equal repulsion
Electron Distribution
(TRIGONAL BIPYRIMIDAL)
Unequal repulsion
Electron Distribution
(TRIGONAL BIPYRIMIDAL)
Unequal repulsion
Electron Distribution
(TRIGONAL BIPYRIMIDAL)
Electron Distribution
(TRIGONAL BIPYRIMIDAL)

13. Linear
Square planar
F
S
SF6
F
F
F
F
F
PCI6
-
P
CI
CI
CI
CI
CI
CI
IF5O
I
O
||
F
F
F
F
F
F

S
F

F
F
F
F
CI
P
CI


CI
CI
CI
CI
I
F
F
F

F
F
::
O
Square pyrimidal

CI
Sb
Sb
CI
CI
CICI
CI
CI
CICI
CI
(SbCI5)2- BrF5
Xe
F
FF
F
Xe
XeF4
F
F
F
Br
F
FF
F
F
Br
 F
F
O
F
F
Xe
||
F
FF
F
O
::
Xe
F
F
F
F
F
Te
F
FF
F
F

Te
F
F
F
F
XeOF4 (TeF5)-
-
-
CICI
I
CICI
(ICI4)- -
:
:
:
:
:
:
::
:
:
:
::
:::
:
::
:
::::
::
:
:
:
:
:
:
:
::
:
:
:
:
::
: :::
:
:
:
:
::
:
::
:
::::
:
::::
::::
:
:
:
::
::
:
:
:
:
:
::::
::::
:
:
:::
::::
:
::
:
:
:
:
:
:
::
:::
::::
:
2-
2-
:
-
-
Lone
Pair
Bonding
Pair
::
::
:
::::
::::
:
: :
:
:
:
:
:
:
:
::
::
:
(XeF3) -
F
(XeF2)2-
F
F
Xe
E
L
E
C
T
R
O
N
C
H
A
R
G
E
C
E
N
T
E
R Lone pair in equatorial first, then axial
Lone pair in equatorial first, then axial
:
:
:
:
-
2-
Minimise repulsion
Minimise repulsion
ECC = 6
6 bond pair
Bond angle
90°
Octahedral ✓
ECC = 6
5 bond pair
1 lone pair
Bond angle
< 90°
✓
4 bond pair
2 lone pair
✓
3 bond pair
3 lone pair
Bond angle
< 90° T shape ✓
2 bond pair
4 lone pair
Bond angle
180°
✓
Equal repulsion
Electron Distribution
(OCTAHEDRAL)
Unequal repulsion
Electron Distribution
(OCTAHEDRAL)
Bond angle
90°
Electron Distribution
(OCTAHEDRAL)
Electron Distribution
(OCTAHEDRAL)
Unequal repulsion
Electron Distribution
(OCTAHEDRAL)

14. Valence Shell Electron Pair Repulsion
Predict molecular shape/geometry Shape determine by electron pairs/
electron charge centers/ECC
Bonding/lone pair – repel each other
Bonding/lone pair arrange themselves as far as possible
(minimise repulsion)
Valence
Shell
Electron
Pair
Repulsion
N
H
HH
..
Principles of VSEPR
Shape of molecule
Determine number valence e around central atom1
2 Single, double, triple bond , lone pair act as electron
charge center/ECC
3
4 Lone pair-lone pair > Lone pair-bonding pair > bonding pair-
bonding pair repulsion
5
6 ECC or electron pair position in equatorial first, then axial
Lewis structure
VSEPR
..
N
H
H
H
Geometry
4 ECC
3 bonding pair
1 lone pair
Trigonal pyrimidal
1
2
3
Bond pair electron
• Occupy smaller region
space bet nuclei
• Repulsion less
Lone pair electron
nucleus
>
Bonding pair electron
Concept Map
nuclei
Lone pair electron
• Electron pair occupy
greater space
• Repel any bonding pair nearby
• Lone pair repulsion > bonding pair repulsion
Double bond
•Repulsion greater
•Angle smaller, 111.4°
B
F
F
F
Single bond
•Equal repulsion
•Angle 120°
120°
120°
120°
space occupy
by electron
space occupy
by electron