Molecular Structure Chemical Bonding and Welcome to

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Chemical Bonding and Molecular Structure

Quick Recap

1

2

3 5

4

Chemical Bond and its Types

Formal Charge

Valence Bond

Theory

Kossel-Lewis Theory

Octet Rule and its

Limitations

Orbital Overlap Concept

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Chemical BondingClip 10_21JEE11CHE04NH

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Ab aap dekhe

sahi honi chahiye

0:01:57

● Covalent bond formation occurs when appropriately oriented atomic orbitals of the combining atoms undergo overlapping

● Each orbital should have one electron with opposite spin

Key Takeaways

Orbital Overlap Concept

Directional Nature of Covalent Bonds


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Clip 11_21JEE11CHE04NHChemical Bonding and Molecular Structure

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Covalent bond jo ban rha h

Thik hai

0:05:20

Key Takeaways

● Positive overlapping

● Negative overlapping

● Zero overlapping

Positive overlapping is allowed while negative and zero overlapping aren’t.

Types of overlaps based on direction:

Covalent Bond

Covalent bond

Sigma (σ) bond Pi (𝛑) bond


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Along the axis

Dikha diya hai

0:03:52

● End to end or head on overlap of the bonding orbitals along the internuclear axis form sigma bond.

Key Takeaways

↿ ⇂ ↿⇂

↿ ⇂ ↿⇂

↿ ⇂ ↿⇂

s s

s p

pp

s-s overlap

s-p overlap

p-p overlap

Key Takeaways

Axial or Head on Overlapping

Can undergo rotation about the internuclear axis

Sigma Bond

Covalent Bond

Covalent bond

Sigma (σ) bond Pi (𝛑) bond


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hum pi bond ki

Jiska hume anumaan hona chahiye

0:04:47

Key Takeaways

● The overlap where the axes of the combining orbitals are perpendicular to the internuclear axis forms pi bond.

+ or

Lateral or Sidewise Overlapping

Cannot undergo rotation about the internuclear axis

𝛑 Bond

Pi (𝛑) Bond

Generally, 𝛑 bond between two atoms is formed in addition to a σ bond

Let Us Solve a Question

TEACHER

Fill the boxes on right based on the type of bond formed:

Orbitals Interacting

Approaching along

Bond Formed

px + px

x-axis

y-axis

z-axis

py + py

x-axis

y-axis

z-axis

In general, 𝛔 bond is stronger than 𝜋 bond


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In general

Ji haan bilkul

0:02:24

● Greater the extent of overlapping between the two atomic orbital, stronger will be the bond.

Key Takeaways

Strength of Different σ bonds

Extent of Overlapping

Less diffused and provide less area for

overlapping

s orbital spherical in

shape


Provides greater area for

overlapping

Directional in Naturep-Orbital

For same value of n

s - s overlap s - p overlap p - p overlap< <

3s - 3s overlap 2s - 2s overlap 1s - 1s overlap< <

For different value of n


Strength of different 𝛑 bonds

2p𝜋 - 2p𝜋 overlap 3p𝜋 - 3p𝜋 overlap>>

Order of Strength of Pi Bonds

(2p𝛑 - 2p𝛑 bond)2p 2p

(3p𝛑- 3p𝛑 bond)3p 3p

Order of Strength of Pi Bonds

Limitations of VBT

Paramagnetic nature of O2could not be

explained

Limitations of VBT

Fails to account for the

geometry and shapes of

various molecules

Limitations of VBT

Valence Shell Electron Pair Repulsion Theory (VSEPR)


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Clip 15_21JEE11CHE04NH

Chemical Bonding and Molecular structure

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Kya khti hai VSEPR theory

Other as possible fine

0:04:34

● Shape of a molecule depends upon the number of valence shell electron pairs around the central atom.

● Valence shell is taken as a sphere with the electron pairs localising on the spherical surface.

● Electron pairs in the valence shell repel one another since they are negatively charged.

● Electron pairs occupy positions in space that tend to minimise repulsion.

Key Takeaways

VSEPR Theory

Let UsContinue...


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Single bond double

Theek hai

0:04:26

● A multiple bond is treated as a single bonding pair.

● Lone pair occupies more space on the sphere. So, the order of repulsion is: lp - lp > lp - bp > bp - bp

(lp - Lone pair, bp - Bonding pair)

Key Takeaways

VSEPR Theory

Shape of Molecules


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(0:14:25 to 0:17:24)

Dhyan Rakhna

Rha hoga

0:02:59

Points to remember

● For electronic geometry, both bond pairs and lone pairs are considered.

● For shape, only bond pairs are considered.

● Lone pairs are not a part of the shape but they can alter the shape.

Key Takeaways

General formula: AB2

Geometry and Shape


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Chemical Bonding and Molecular structure(0:18:03 to 0:20:32)

Humare pas A jo h

Issi category me aa jate h

0:02:29

Molecular shape of AB2:

Key Takeaways

Examples: CO2, BeCl2

Bond Angle = 180o

General formula: AB3 and AB2L

Geometry and Shape


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Agar AB3 ho

Angular ya bent

0:04:34

Molecular shape of AB3:

Key Takeaways

Examples: BF3, SO3

Bond Angle = 120o

Molecular shape of AB2L:

Key Takeaways

Examples: SO2, SnCl2

Bond Angle < 120o


Electron pairs

Bonding pairs

Lone pairs

Electronic Geometry Shape

4 4 0 Tetrahedral Tetrahedral

VSEPR

VSEPR

Examples: CH4, NH4, XeO4

Bond Angle = 109.5o

VSEPR

General formula: AB3L

Electron pairs

Bonding pairs

Lone pairs


4 3 1 Tetrahedral Pyramidal

VSEPR

Examples: NH3, XeO3, PCl3

Bond Angle < 109.5o

VSEPR

General formula: AB2L2

Electron pairs

Bonding pairs

Lone pairs


4 2 2 Tetrahedral Bent or V shape

VSEPR

Example : H2O

Bond Angle < 109.5o

VSEPR


Electron pairs

Bonding pairs

Lone pairs


5 5 0 Trigonal Bipyramidal

Trigonal Bipyramidal

VSEPR

Example : PCl5

Bond Angle = 90o, 120o, 180o

VSEPR


Electron pairs

Bonding pairs

Lone pairs


5 4 1 Trigonal Bipyramidal See saw

VSEPR

Example : SF4

Bond Angle < 90o, 120o, 180o

VSEPR


Electron pairs

Bonding pairs

Lone pairs


5 3 2 Trigonal Bipyramidal T shape

VSEPR

Example : ClF3

Bond Angle < 90o, 180o

VSEPR


Electron pairs

Bonding pairs

Lone pairs


5 2 3 Trigonal Bipyramidal Linear

VSEPR

Example : XeF2

Bond Angle 180o=

VSEPR


Electron pairs

Bonding pairs

Lone pairs


6 6 0 Octahedral Octahedral

VSEPR

Example : SF6

Bond Angle = 90o , 180o


Electron pairs

Bonding pairs

Lone pairs


6 5 1 Octahedral Square Pyramidal

VSEPR

VSEPR

Example : BrF5

Bond Angle < 90o , 180o

VSEPR


Electron pairs

Bonding pairs

Lone pairs


6 4 2 Octahedral Square Planar

VSEPR

Example : XeF4

Bond Angle = 90o, 180o

VSEPR


Electron pairs

Bonding pairs

Lone pairs


7 7 0 Pentagonal bipyramidal

Pentagonal bipyramidal

Example: IF7

Bond Angle 72o, 144o, 90o, 180o

VSEPR

=

VSEPR


Electron pairs

Bonding pairs

Lone pairs



Distorted Octahedral

Example: XeF6

VSEPR

VSEPR


Electron pairs

Bonding pairs

Lone pairs



Pentagonal Planar

Example: XeF5-

Bond Angle 72o, 144o

VSEPR

=

A Linear and Distorted Octahedral

B See saw and Linear

C T-Shaped and Trigonal Bipyramidal

D Tetrahedral and Linear

The shapes of SF4 and XeF2 respectively are:

The shapes of SF4 and XeF2 respectively are:

A Linear and Distorted Octahedral

B See saw and Linear

C T-Shaped and Trigonal Bipyramidal

D Tetrahedral and Linear

A

B

C

D

XeF2O2

PCl5

AsH4

XeF4

In which of the following species maximum atom can lie in same plane?

A

B

C

D

XeF2O2

PCl5

XeF4

In which of the following species maximum atom can lie in same plane?

AsH4

Molecular shapes of SF4, CF4 and XeF4 are:

A

B

C

D

The same, with 2, 0 and 1 lone pair of electrons respectively


Different, with 0, 1 and 2 lone pair of electrons respectively


A

B

C

D





Molecular shapes of SF4, CF4 and XeF4 are:

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