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IB Chemistry on Valence Bond and Hybridization Theory
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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 Bonding
CI CI
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
:
. 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
: Be CI CI
x . :
: :
: :
x
x .
Be - 4 valence e
B CI CI : : : :
: :
x
: : B - 6 valence e
P S
CI
CI
CI
CI
CI
CI
CI CI
CI CI CI
P - 10 valence e
S – 12 valence e
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 H H
.. Principles of VSEPR
Shape of molecule
Determine number valence e around central atom 1
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
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 atom 1
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
H H H
3 bonding pair
1 lone pair 4 ECC
N – central atom
3 ECC
C H
= O H
H C N
2 ECC
O H H
4 ECC
> > 1 lone pair 2 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 repulsion Equal repulsion
90°
120°
109.5°
107°
180°
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 H H
..
Principles of VSEPR
Shape of molecule
Determine number valence e around central atom 1
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
Valence
Shell
Electron
Pair
Repulsion
N
H H H
.. Shape of molecule
.. N
H H
H
Geometry
4 ECC
3 bonding pair
1 lone pair
Trigonal pyrimidal
1 2 3 Lewis Theory VSEPR
Valence Bond Theory
- Atomic orbital overlap - Electron localized in overlap region - Electron density between nuclei
- Lewis structure - Valence electron involve in bonding - Localized region space - Sharing of valence electron
Using VSEPR
predict shape
Shape Molecule
Quantum mechanics approach
1s orbital 1s orbital
1s orbital 2p orbital
2p orbital 2p orbital
Localized
electron pair
Electron density/cloud
1s 1s Attraction bet nuclei
with electron cloud
Minimum energy, most stable, bond length
Too near repulsion bet +ve nuclei
Atomic Orbitals
n= 1
n= 2
l=0 1s sublevel
l=0
l=1
2s sublevel
2p sublevel
n= 3
l=1
l=2
l=0 3s sublevel
3p sublevel
3d sublevel
ml =0
ml =0
ml = 0
ml =-1
ml =+1
ml = 0
ml = 0
ml =-1
ml =+1
ml =+1
ml =-1
ml =+2
ml =-2
ml = 0
1s orbital
2s orbital
2px orbital
2py orbital
2pz orbital
3s orbital
3px orbital
3py orbital
3pz orbital
3dxy orbital
3dxz orbital
3dyz orbital
3dz2 orbital
3dx2 – y
2orbital
Click here to view simulation
Energy Level
Valence Bond Theory
Atomic orbital overlap Electron localized in overlap region Electron density bet nuclei
1s orbital 1s orbital
2p orbital 1s orbital
2p orbital 2p orbital Localized
electron pair
Click here hybridization notes
Click here orbital overlap
sigma bond
Valence Bond Theory
overlap
Molecular orbital sigma bond
Sigma σ bond • 2 atomic orbital overlap • End to end overlap along internuclear axis • Overlap of orbitals between nuclei • Constructive interference
Pi π bond • 2 p orbital overlap sideways • Overlap of unhybridized/parallel p orbital • Parallel p orbital overlaps • Sideway interaction of 2 p orbitals
+
Atomic orbital overlap
+
internuclear axis
overlap
Atomic orbital overlap
+ +
Molecular orbital pi bond
+
Sigma bond stronger- greater orbital overlap Pi bond weaker - less orbital overlap
One s orbital + One p orbital → TWO sp hybrid orbital
Hybridization Theory
Mixing of atomic orbital to form new hybrid orbital for bonding Atomic orbital + Atomic orbital → Hybrid orbital
+
One s orbital + Two p orbital → THREE sp2 hybrid orbital
+ +
One s orbital + Three p orbital → FOUR sp3 hybrid orbital
+ + +
Correlation between VSEPR and Hybridization Theory
Formula
Lewis Structure
VSEPR
Hybridization
NH3 1
2
3
4
H
H
H
VSEPR Electron Domain
Electron charge center
Hybridization
2 sp
3 sp2
4 sp3
5 dsp3
6 d2sp3
1
2
3
4
Atomic orbital
Type of Hybridization
Number Hybrid orbitals
VSEPR Number Electron domain
VSEPR Electron geometry domain
s,p sp 2 2 Linear
s,p,p sp2 3 3 Trigonal planar
s,p,p,p sp3 4 4 Tetrahedral
s,p,p,p,d dsp3 5 5 Trigonal Bipyrimidal
s,p,p,p,d,d d2sp3 6 6 Octahedral
Relationship between VSEPR and Hybridization
25% s character
75% p character
33% s character
66% p character
50% s character
50% p character
Click here for simulation
✓ Excellent simulation
Valence
Shell
Electron
Pair
Repulsion
N
H H H
.. Shape of molecule
.. N
H H
H
Geometry
4 ECC
3 bonding pair
1 lone pair
Trigonal pyrimidal
1 2 3 Lewis Theory VSEPR
Valence Bond Theory
- Atomic orbital overlap - Electron localized in overlap region - Electron density between nuclei
- Lewis structure - Valence electron involve in bonding - Localized region space - Sharing of valence electron
Using VSEPR
predict shape
Shape Molecule
- Quantum mechanics approach - Strength covalent bond proportional to overlap bet orbitals - Greater overlap – stronger bond - Atom undergo hybridization to maximize overlap - Wave combine constructive/destructively form hybrid orbital
1s orbital 1s orbital
1s orbital 2p orbital
2p orbital 2p orbital
Localized
electron pair
Orbital - Probability of finding electron in a region space - Cloud of probability - Not possible determine exact location electron - Electron density
Electron cloud
1s
sp hybridization, Beryllium hydride, BeH2
1s
2s
2p
4Be - 1s2 2s2
1s
2p
High energy
Ground state Excited state
excited
Hybridized state
sp sp
2py 2pz
2s
sp
hybridization
+
s orbital p orbital sp hybrid orbital
+ + Be
H – Be - H
sp2 hybridization Boron hydride, BH3
High energy
5B - 1s2 2s3
Ground state
2s
1s
2p
1s
2s
2p
1s
2p
excited
+ +
sp2
hybridization
sp2 sp2 sp2
B
Excited state Hybridized state
Be – sp hybridization
B – sp2 hybridization
B
- TWO sp hybrid orbitals
- Linear electron distribution
- 2 bonding pair
- sp orbital Be overlap
with s orbital hydrogen
- THREE sp2 hybrid orbitals
- Trigonal electron distribution
- 3 bonding pair
- sp2 orbital B overlap
with s orbital hydrogen
B
H
H H
1s
sp3 hybridization methane, CH4
1s
2s
2p
6C - 1s2 2s22p2
1s
2p
Ground state Excited state
excited
Hybridized state
2s
sp3
hybridization
+
sp3 hybridization ammonia NH3
Ground state
2s
1s
2p
1s
2s
2p
1s
excited
+
sp3
hybridization
sp3 sp3 sp3
Excited state Hybridized state
sp3 sp3 sp3 sp3
C
+
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 4 bonding pair
- sp3 orbital carbon overlap
with s orbital hydrogen
7N - 1s2 2s22p3
sp3
+
NH3
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 3 Bonding pair/1 lone pair
- sp3 orbital nitrogen overlap
with s orbital hydrogen
CH4
2p
2s
1s
2p
1s
sp2 hybridization ethene, C2H4
1s
2s
2p
6C - 1s2 2s22p4
1s
2p
Ground state Excited state
excited
Hybridized state
2s
sp2
hybridization
+
sp2 sp2 sp2
unhybridized
2p orbital
C2H4
sp hybridization ethyne, C2H2
6C - 1s2 2s22p4
Ground state
1s
2s sp
hybridization
+
unhybridized
2p orbital
sp sp
unhybridized 2p orbital
overlap form π bond
unhybridized 2p orbital
overlap form π bond
π bond
Click here to view hybridization Click here hybridization theory
Video on hybridization
C
C
2p
2s
1s
2p
1s
sp2 hybridization methanal, H2CO
1s
2s
2p
6C - 1s2 2s22p4
1s
2p
Ground state Excited state
excited
Hybridized state
2s
sp2
hybridization
+
sp2 sp2 sp2
unhybridized
2p orbital
6C - 1s2 2s22p4
Ground state
1s
2s sp
hybridization
+
unhybridized
2p orbital
sp sp
unhybridized 2p orbital
overlap form π bond
unhybridized 2p orbital carbon
overlap form π bond
sp hybridization carbon dioxide, CO2
C
sp hybridization C
sp2 hybridization O
C C
Oxygen
sp2 hybridization
1s
sp3 hybridization water H2O
1s
2s
2p
8O - 1s2 2s22p4
1s
2p
excited
2s
sp3
hybridization
+
sp3 hybridization phosphorus trichloride PCI3
Ground state
2s
1s
2p
1s
2s
2p
1s
excited
+
sp3 sp3 sp3
Excited state Hybridized state
sp3 sp3 sp3 sp3
O
+
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 2 bonding pair/ 2 lone pair
- sp3 orbital oxygen overlap
with s orbital hydrogen
15P - 1s2 2s22p63s23p3
sp3
+
PCI3
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 3 bonding pair/1 lone pair
- sp3 orbital phosphorus overlap
with p orbital chlorine
H2O
3s
3p
3s
3p
2s
2p
sp3
hybridization CI 3p
P
P
P
O
H H
CI CI
CI
:
1s 1s
2p
excited
2s
sp3
hybridization
dsp3 hybridization phosphorus pentachloride PCI5
Ground state
2s
1s
2p
1s
2s
2p
1s
excited
Excited state Hybridized state
sp3
15P - 1s2 2s22p63s23p3
PCI3
- Five dsp3 hybrid orbitals
- Trigonal bipyrimidal electron distribution
- 5 Bonding pair
- dsp3 orbital phosphorus overlap with p orbital chlorine
3s
3p
3s
3p
2s
2p
dsp3
hybridization
CI 3p
P
P
CI CI
CI 1s
2s
2p
3s
3p
3s
3p
2s
2p
sp3 sp3 sp3
CI 3p
+
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 3 bonding pair/1 lone pair
- sp3 orbital phosphorus overlap
with p orbital chlorine
P
3d 3d
5 dsp3
+
Phosphorus exist as PCI3 or PCI5
sp3 hybridization phosphorus trichloride PCI3
Expanded Octet ✓
P
Click here to view
:
1s 1s
2p
excited
2s
sp3
hybridization
dsp3 hybridization SF4
Ground state
2s
1s
2p
1s
2s
2p
1s
excited
Excited state Hybridized state
sp3
15S - 1s2 2s22p63s23p6
SF2
- Five dsp3 hybrid orbitals
- Trigonal bipyrimidal electron distribution
- 4 bonding pair/1 lone pair
- dsp3 orbital sulfur overlap with p orbital fluorine
3s
3p
3s
3p
2s
2p
dsp3
hybridization
F 3p
S
S
F F
1s
2s
2p
3s
3p
3s
3p
2s
2p
sp3 sp3 sp3
F 3p
+
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 2 bonding pair/2 lone pair
- sp3 orbital sulfur overlap
with p orbital fluorine
S
3d 3d
5 dsp3
+
Sulfur exist as SF2, SF4 or SF6
sp3 hybridization SF2
Expanded Octet
F
F
F
F
S
SF4
:
S
✓
1s 1s
2p
excited
2s
sp3
hybridization
d2sp3 hybridization SF6
Ground state
2s
1s
2p
1s
2s
2p
1s
excited
Excited state Hybridized state
sp3
15S - 1s2 2s22p63s23p6
SF2
- Six d2sp3 hybrid orbitals
- Octahedral electron distribution
- 6 Bonding pair
- d2sp3 orbital sulfur overlap with p orbital fluorine
3s
3p
3s
3p
2s
2p
d2sp3
hybridization
F 3p
S
1s
2s
2p
3s
3p
3s
3p
2s
2p
sp3 sp3 sp3
F 3p
+
- Four sp3 hybrid orbitals
- Tetrahedral electron distribution
- 2 Bonding pair/2 lone pair
- sp3 orbital sulfur overlap
with p orbital fluorine
S
3d 3d
6 d2sp3
+
Sulfur exist as SF2, SF4 or SF6
sp3 hybridization SF2
Expanded Octet
SF6
3d
F F
S :
S
✓
IB Question
State the type of hybridization shaded in red
CO2 SO3 SO2
CH4
NH3 H2O H2CO CH3COOH
XeF2 CIF3 CO32- NO2
- BrF5 XeF4
sp
:
sp2 sp2 sp3 sp2 sp3 sp2
sp2 sp2 d2sp3 dsp3 dsp3 d2sp3 sp3
State the hybridization shaded in red and number of sigma and pi bonds
sigma bonds pi bond
C- sp2
N- sp3 : :
: :
C C :
N- sp3 N- sp3
C- sp2 C- sp2
C - sp3
19 sigma bonds
2 pi bonds
12 sigma bonds
2 pi bonds
5 sigma bonds
1 pi bond
C- sp2
C- sp3
ECC Bonding
Pair
Lone
Pair
Electron Distribution
Electron geometry domain
Hybridization
s, p
VSEPR
Atomic
orbitals
Type of
Hybridization
sp
Number of
Hybrid orbitals
s, p, p
s, p, p, p
s, p, p, p, d
s, p, p, p, d, d
sp2
sp3
dsp3
d2sp3
linear
Trigonal
planar
Tetrahedral
Trigonal
Bipyrimidal
Octahedral
Shape/Geometry
linear
s, p, p sp2 Trigonal
planar
Tetrahedral
Tetrahedral
s, p, p, p
s, p, p, p
sp3
sp3
..
Trigonal
Bipyrimidal s, p, p, p, d dsp3
Trigonal
Bipyrimidal s, p, p, p, d dsp3
Trigonal
Bipyrimidal s, p, p, p, d dsp3
Octahedral
Octahedral
s, p, p, p, d, d
s, p, p, p, d, d
d2sp3
d2sp3 ..
..
..
..
..
Trigonal
planar
Bend
V shape
Tetrahedral
Trigonal
pyrimidal
Bend
V shape
Trigonal
Bipyrimidal
Seesaw
T shape
Linear
Octahedral
Square
pyrimidal
Square
planar
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