ib chemistry on valence bond and hybridization theory

http://lawrencekok.blogspot.com

Prepared by Lawrence Kok

Tutorial on Valence Bond Theory and Hybridization.

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 BondingElectrostatic 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

CICI

Lewis structure/diagram . Electron cross dot . Valence/bonding pair electron

CI CI: xx:

:

:.

xx

X

xx

xx CI CI

:: xx

xx

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


CI CI: xx

::

:

:.

xx

X

X

xx

xx

O

CI CI:

: xxxx

xx

CI CI

:O O: : x

x

xx

xx

O:

: xx

xx

N

O O

N:



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 order up – Bond strength up – Bond length down

O:

Non bonding pair (Lone pair electron)

Bonding pair electron

C O: :


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 deficientLess than 8 valence e

Expanded octetMore 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

CICICI

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

HHH

..

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

HH

H

Shape

Click here VSEPR simulation

..



Principles of VSEPR


1


3 Bonding/lone pair repel each otherLone /lone pair > Lone /bond pair > bond/bond pair repulsion

4

5

For 5/6 ECC:ECC position in equatorial first, then axial

..

NHHH

3 bonding pair

1 lone pair4 ECC

N – central atom

3 ECC

CH

=OH

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 spaceMultiple bonds more space

Unequal repulsion

Equal repulsion

90°120°

109.5°

107°

180°


Predict molecular shape/geometry

Shape determine by electron pairs/ electron charge centers/ECC

Bonding/lone pair – repel each other


Valence

Shell

Electron

Pair

Repulsion

N

HHH

..

Principles of VSEPR

Shape of molecule


1


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

HH

H

Geometry

4 ECC

3 bonding pair1 lone pair

Trigonal pyrimidal

1

2

3

Bond pair electron •Occupy smaller region space bet nuclei•Repulsion less

Lone pair electron

nucleus

>


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

HHH

..

Shape of molecule

..N

HHH

Geometry

4 ECC


Trigonal pyrimidal

1 2 3

- 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

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

Atomic orbital overlapElectron localized in overlap region Electron density bet nuclei

1s orbital1s orbital

2p orbital1s orbital

2p orbital 2p orbital Localized electron pair

Click here hybridization notes

Click here orbital overlap

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

+

overlap


+ +

Molecular orbital pi bond

sigma bond

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

+


+

internuclear axis

overlap


+ +

Molecular orbital pi bond

+

Sigma bond stronger- greater orbital overlap Pi bond weaker - less orbital overlap

Formula

Lewis Structure

VSEPR

Hybridization

NH31

2

3

4

HH

H

One s orbital + One p orbital → TWO sp hybrid orbital

Mixing of atomic orbital to form new hybrid orbital for bondingAtomic 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

+ + +

Formula

Lewis Structure

VSEPR

Hybridization

NH31

2

3

4

HH

H

1

2

3

4

25% s character75% p character



One s orbital + One p orbital → TWO sp hybrid orbital

Mixing of atomic orbital to form new hybrid orbital for bondingAtomic 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

+ + +

Formula

Lewis Structure

VSEPR

Hybridization

NH31

2

3

4

HH

H

VSEPRElectron DomainElectron charge

center

Hybridization

2 sp

3 sp2

4 sp3

5 dsp3

6 d2sp3

1

2

3

4

Atomic orbital

Type ofHybridization

NumberHybrid orbitals

VSEPRNumber Electron domain

VSEPRElectron geometrydomain

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 TrigonalBipyrimid

al

s,p,p,p,d,d

d2sp3 6 6 Octahedral




Click here for simulation

✓Excellent simulation

Valence

Shell

Electron

Pair

Repulsion

N

HHH

..

Shape of molecule

..N

HHH

Geometry

4 ECC


Trigonal pyrimidal

1 2 3

- Lewis structure- Valence electron involve in

bonding- Localized region space- Sharing of valence electron


Valence

Shell

Electron

Pair

Repulsion

N

HHH

..

Shape of molecule

..N

HHH

Geometry

4 ECC


Trigonal pyrimidal

1 2 3

- 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


- 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 sp2py 2pz

2s

sp hybridization

+

s orbital p orbitalsp hybrid orbital

+ +Be

H – Be - H

Be – sp hybridization

- TWO sp hybrid orbitals- Linear electron distribution- 2 bonding pair- sp orbital Be overlap with s orbital hydrogen

1s

sp hybridization, Beryllium hydride, BeH2

1s

2s

2p

4Be - 1s2 2s2

1s

2p

High energy


excited

Hybridized state

sp sp2py 2pz

2s

sp hybridization

+

s orbital p orbitalsp 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 sp2sp2

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

HH

1s

sp3 hybridization methane, CH4

1s

2s

2p

6C - 1s2 2s22p2

1s

2p


excited

Hybridized state

2s

sp3

hybridization

+

sp3 sp3 sp3 sp3

C+

- Four sp3 hybrid orbitals- Tetrahedral electron distribution- 4 bonding pair- sp3 orbital carbon overlap with s orbital hydrogen

CH4

1s

sp3 hybridization methane, CH4

1s

2s

2p

6C - 1s2 2s22p2

1s

2p


excited

Hybridized state

2s

sp3

hybridization

+

sp3 hybridization ammonia NH3

Ground state

2s

1s

2p

1s

2s

2p

1s

excited

+

sp3

hybridization

sp3 sp3sp3


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

1s

sp2 hybridization ethene, C2H4

1s

2s

2p

6C - 1s2 2s22p4

1s

2p


excited

Hybridized state

2s

sp2

hybridization

+

sp2 sp2 sp2

unhybridized 2p orbital

C2H4

unhybridized 2p orbital overlap form π bond

C

2p

2s

1s

2p

1s

sp2 hybridization ethene, C2H4

1s

2s

2p

6C - 1s2 2s22p4

1s

2p


excited

Hybridized state

2s

sp2

hybridization

+

sp2 sp2 sp2


C2H4

sp hybridization ethyne, C2H2

6C - 1s2 2s22p4

Ground state

1s

2s sp hybridization

+


sp sp



π bond

Click here to view hybridization Click here hybridization theory

Video on hybridization

C

C

1s

sp2 hybridization methanal, H2CO

1s

2s

2p

6C - 1s2 2s22p4

1s

2p

Ground stateExcited state

excited

Hybridized state

2s

sp2

hybridization

+

sp2 sp2 sp2



CC

Oxygen sp2 hybridization

2p

2s

1s

2p

1s

sp2 hybridization methanal, H2CO

1s

2s

2p

6C - 1s2 2s22p4

1s

2p

Ground stateExcited state

excited

Hybridized state

2s

sp2

hybridization

+

sp2 sp2 sp2


6C - 1s2 2s22p4

Ground state

1s

2s sp hybridization

+


sp sp


unhybridized 2p orbital carbon overlap form π bond

sp hybridization carbon dioxide, CO2

C

sp hybridization C

sp2 hybridization O

CC

Oxygen sp2 hybridization

1s

sp3 hybridization water H2O

1s

2s

2p

8O - 1s2 2s22p4

1s

2p

excited2s

sp3

hybridization

+

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

H2OO

H H

: :

1s

sp3 hybridization water H2O

1s

2s

2p

8O - 1s2 2s22p4

1s

2p

excited2s

sp3

hybridization

+

sp3 hybridization phosphorus trichloride PCI3

Ground state

2s

1s

2p

1s

2s

2p

1s

excited

+

sp3 sp3sp3


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

CICI

CI

: :

:

1s1s

2p

excited

2s

sp3

hybridizationsp3

PCI3

PCI

CICI1s

2s

2p

3s

3p

3s

3p

2s

2p

sp3 sp3 sp3

CI 3p

+


P

Phosphorus exist as PCI3 or PCI5


:

1s1s

2p

excited

2s

sp3

hybridization

dsp3 hybridization phosphorus pentachloride PCI5

Ground state

2s

1s

2p

1s

2s

2p

1s

excited


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

3s3p

2s

2p

dsp3

hybridization

CI 3p

P

PCI

CICI1s

2s

2p

3s

3p

3s

3p

2s

2p

sp3 sp3 sp3

CI 3p

+


P

3d 3d

5 dsp3

+

Phosphorus exist as PCI3 or PCI5


Expanded Octet✓

P

Click here to view

:

1s1s

2p

excited

2s

sp3

hybridizationsp3

SF2

S

FF

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

Sulfur exist as SF2, SF4 or SF6

sp3 hybridization SF2

:

:

1s1s

2p

excited

2s

sp3

hybridization

dsp3 hybridization SF4

Ground state

2s

1s

2p

1s

2s

2p

1s

excited


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

3s3p

2s

2p

dsp3

hybridization

F 3p

S

S

FF

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

+



Expanded Octet

FF

FF

S

SF4

:

:

S

✓

1s1s

2p

excited

2s

sp3

hybridizationsp3

SF2

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



FF

:

S :

1s1s

2p

excited

2s

sp3

hybridization

d2sp3 hybridization SF6

Ground state

2s

1s

2p

1s

2s

2p

1s

excited


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

3s3p

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

+



Expanded Octet

SF6

3d

FF

:

S :

S

✓

IB Question

State the type of hybridization shaded in red

CO2SO3 SO2

CH4

NH3 H2O H2COCH3COOH

XeF2 CIF3CO32- NO2

- BrF5 XeF4

:

State the hybridization shaded in red and number of sigma and pi bonds

sigma bonds pi bond

:

: :

: :

CC :

IB Question

State the type of hybridization shaded in red

CO2SO3 SO2

CH4

NH3 H2O H2COCH3COOH

XeF2 CIF3CO32- 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- sp2N- sp3

:

: :

: :

CC :

N- sp3 N- sp3

C- sp2C- sp2

C - sp3

19 sigma bonds 2 pi bonds

12 sigma bonds 2 pi bonds

5 sigma bonds1 pi bond

C- sp2

C- sp3

ECCBonding Pair

Lone Pair

Electron DistributionElectron geometry domain

Hybridization

s, p

VSEPR

Atomic orbitals

Type ofHybridization

sp

Number ofHybrid 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

TrigonalBipyrimidal

Octahedral

Shape/Geometry

linear

s, p, p sp2Trigonal planar

Tetrahedral

Tetrahedral

s, p, p, p

s, p, p, p

sp3

sp3

..

TrigonalBipyrimidal s, p, p, p, d dsp3



.. ..

Octahedral

Octahedral

s, p, p, p, d, d

s, p, p, p, d, d

d2sp3

d2sp3..

....

......

..

....

:

Trigonal planar

BendV shape

Tetrahedral

Trigonalpyrimidal

BendV shape

TrigonalBipyrimidal

Seesaw

T shape

Linear

Octahedral

Squarepyrimidal

Square planar

Acknowledgements

Thanks to source of pictures and video used in this presentation

Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/

Prepared by Lawrence Kok

Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com

ib chemistry on valence bond and hybridization theory

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