valence shell electron pair repulsion theory

Kips Unit 4, UHS Topic 4(A), 2 MCQ’s

Contents• VSEPR Theory• VBT• Hybridization• Bond energy, Bond

length• Bond Polarity

Chemical Bonding

Muhammad Farooq Mukhtar

Valence Shell Electron Pair Repulsion Theory

Features• Only applicable for AB2 and above

systems.• Molecular geometry depends on

both lp and bp of e’s.• Maximum separation between

electron pairs to minimize repulsions.

• Space occupied: lp > bp

• lp- lp > lp- bp > bp- bp

In ABx type molecule B representsA. Bond pairsB. Lone pairsC. Electron pairsD. Bonded atoms

KIPS UNIT 4, UHS TOPIC 4(A), 2 MCQ’s



Type Total e pairs Bond pairs Lone pairs Electronic

geometryMolecular geometry Angle Example

AB2 2 2 - Linear Linear 180o

AB3 3

3 -

Triangular planner

Triangular planner 120o

2 1 BentLess than 120o

http://people.bath.ac.uk/ch3tam/inorganic/vsepr/movies/SnCl2.mov

http://people.bath.ac.uk/ch3tam/inorganic/vsepr/movies/BF3.mov



Type Total e pairs Bond pairs Lone pairs Electronic

geometryMolecular geometry Angle Example

AB4 4

4 -

Tetrahedral

Tetrahedral 109.5o

3 1 Trigonal pyramidal

Less than

109.5o

2 2 BentLess than

109.5o

http://people.bath.ac.uk/ch3tam/inorganic/vsepr/movies/NH3.mov

http://people.bath.ac.uk/ch3tam/inorganic/vsepr/movies/CH4.mov


All are incorrect statements about bond angle in NH3 & NF3 excepts

A. Both have 104.5o

B. Both have 107.5o

C. NF3 has greater bond angle

D. NH3 has greater bond angle


Pick the one with bent shapeA. CO2

B. SnCl2

C. CS2

D. HgCl2

The H-O-H bond angle in H2O(s)

isA. 104.5o

B. 107.5o

C. 109.5o

D. Less than 104.5o

H2S & H2O has same hybridization and no of lone pairs. Select the correct option about bond angle

A. Both have same bond angleB. H2S has greater bond angle

C. H2O has greater bond angle

D. Difficult to predict


Valence Bond Theory

Bond formation

No of bonds = unpaired e’s

Overlapping of atomic orbitals

Strength of bond α extent of overlapping

Which one will result in stronger covalent bondA. s-s overlapB. s-p overlapC. p-p overlapD. All have same strength

All statements are correct about VBT exceptA. No idea about paramagnetismB. Justifies valencies of all elementsC. Colour of complexes is not

explainedD. Maximum sigma bonds b/w two

atoms is always one


Valence Bond Theory

Formation of s bond


Valence Bond Theory

s bond


Sidewise overlapping


Sidewise overlapping

Planar molecule with p cloud above and below the plane


Formation of p Bond

Hybridization

Features• Intermixing of atomic orbitals of

slightly different energy and shapes to form hybrid orbitals of same energy and shape.

• No of hybrid orbitals = No of atomic orbitals intermixed

• Occupied by lp and bp of sigma bond

• It decreases reactivity of molecules.


Hybridization


Property sp3 sp2 sps-orbitals 1 1 1

p-orbitals 3 2 1

Hybrid orbitals 4 3 2

% s character 25 % 33 % 50 %

% p character 75 % 66 % 50 %

Unhybrid orbitals 0 1 2

Sigma bonds 4 3 2

Pi bonds 0 1 2

Geometry Tetrahedral Triangular planner Linear

Bond angle 109.5o 120o 180o

Example CH4, CCl4 BF3, AlCl3 BeCl2, CO2

sp3 Hybridization


sp2 Hybridization


sp Hybridization


Overlap of Be and Cl orbitals to form BeCl2

Which hybridized carbon is more electronegativeA. sp3 hybridizedB. sp2 hybridizedC. sp hybridizedD. Electron attracting power of

C-atom is always same


Which one the following has only sigma bonds

A. Acetic acidB. Ethyl alcoholC. PropeneD. Benzene

The hybrid state of S in SO3 is similar to C atom in

A. C2H2

B. C2H6

C. CO2

D. C2H4

The pair having similar geometry is

A. BF3 , NH3

B. BeF2 , H2O

C. BF3 , AlCl3

D. BF3 , PCl3

Hybridization

Bond Energy & Bond Length


Bond Energy

Directly related toi) ∆ E.N

ii) % s characteriii) B.O

Inversely related toi) Size

ii) Lone pairsiii) B.L



Bond Length

Inversely related toi) ∆ E.N

ii) % s characteriii) B.O

Directly related toi) Size

ii) Lone pairs

Which of the following overlap will result in minimum bond lengthA. sp3 – s overlapB. sp2 – s overlapC. sp – s overlapD. p-p overlap


Minimum bond energy is observed in which of the following

A. HFB. HClC. HBrD. HI

Maximum bond energy is in the case of

A. C-CB. N-NC. O-OD. F-F


No lone pair in CA- 348 Kjmol-1

B- 163 Kjmol-1

C- 146 Kjmol-1

D- 139 Kjmol-1

A- 566 Kjmol-1

B- 431 Kjmol-1

C- 366 Kjmol-1

D- 299 Kjmol-1

Dipole Moment


Features• Mathematical determination of polarity of bond.

µ = q × rUnits: (SI Unit = Cm) (Derived Unit = Debye)

1D = 3.336 × 10-30 Cm• %age ionic character = µobserved ÷ µionic × 100• Geometry of molecule

Atomicity µ = 0 µ ǂ 0

AB2 Linear -

AB3 Triangular Planner Bent

AB4 Tetrahedral Pyramidal, Bent

Which of the following is non-polar but contains polar bondsA. H2O

B. SO2

C. CS2

D. All are polar


Which of the following isomer of xylene posses maximum polarity

A. B.

C. D. All same

Which one has zero dipole momentA. B.

C. D. All same

Dipole Moment

QUESTIONS

valence shell electron pair repulsion theory

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