Atul Singhal

INORGANIC CHEMISTRY
for the

Advanced

This book is designed to help aspiring engineers understand the various
important aspects of ‘inorganic chemistry’. Each book in this series approaches
the subject in a very conceptual and coherent manner. The illustrative approach
adopted in this series will help students to familiarize themselves with complex
concepts and their applications in a simple manner. This book also includes a
wide variety of questions.

The Pearson Guide to

INORGANIC
CHEMISTRY
for the
JEE Advanced

for the JEE Advanced

SALIENT FEATURES
● 1750+ Multiple-Choice Questions for practice
● Hints and solutions provided for most of the questions
● Follows the latest pattern of JEE Advanced
● Provides extensive pedagogy to demystify the examination pattern

INORGANIC CHEMISTRY

JEE

The Pearson Guide to

The Pearson Guide to

Singhal

Atul Singhal
www.pearson.co.in

Size: 165x229mm

Spine : 20 mm

ISBN : 9789332520899

Title

Sub Title

Edition

Authors / Editors Name

With CD

Red Band

Territory line


URL

Price

mQuest


www.pdfgrip.com

The Pearson Guide to

Inorganic Chemistry
for the

JEE Advanced

A01_Pearson Guide to Inorganic Chemistry_FM.indd i

3/27/2014 12:11:19 PM


www.pdfgrip.com

This page is intentionally left blank.

A01_Pearson Guide to Inorganic Chemistry_FM.indd ii

3/27/2014 12:11:20 PM



www.pdfgrip.com

The Pearson Guide to

Inorganic Chemistry
for the

JEE Advanced
(Also for Indian Science Engineering Eligibilty Test / Joint Entrance Examination)

Atul Singhal

A01_Pearson Guide to Inorganic Chemistry_FM.indd iii

3/27/2014 12:11:20 PM


www.pdfgrip.com

Copyright © 2014 Dorling Kindersley (India) Pvt. Ltd.
Licensees of Pearson Education in South Asia
No part of this eBook may be used or reproduced in any manner whatsoever without the publisher’s
prior written consent.
This eBook may or may not include all assets that were part of the print version. The publisher
reserves the right to remove any material in this eBook at any time.
ISBN 9789332520899
eISBN 9789332537095
Head Office: A-8(A), Sector 62, Knowledge Boulevard, 7th Floor, NOIDA 201 309, India
Registered Office: 11 Community Centre, Panchsheel Park, New Delhi 110 017, India


A01_Pearson Guide to Inorganic Chemistry_FM.indd iv

3/27/2014 12:11:20 PM


www.pdfgrip.com

Dedicated to
My Grand Parents, Parents and Teachers

A01_Pearson Guide to Inorganic Chemistry_FM.indd v

3/27/2014 12:11:20 PM


www.pdfgrip.com

This page is intentionally left blank.

A01_Pearson Guide to Inorganic Chemistry_FM.indd vi

3/27/2014 12:11:20 PM


www.pdfgrip.com

Contents
Preface
Acknowledgements


1.

Chemical Bonding
Chemical Bond
Ionic or Kernel Bond
Covalent Bond
Coordinate or Dative Semi-polar Bond
Modern Concept of Covalent Bond
Polorization and Fajan’s Rule
Sigma and Pi Bonds
Hydrogen Bond
Hybridization
Molecular Orbital Theory
Some Important Guidelines
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

2.

xi
xii

1.1
1.2
1.4
1.5
1.5

1.9
1.12
1.13
1.16
1.21
1.26

Periodic Properties
Long Form of Periodic Table
Type of Elements
Trends in Periodic Properties of Elements
Unforgettable Guidelines
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

A01_Pearson Guide to Inorganic Chemistry_FM.indd vii

2.2
2.2
2.4
2.11

3/27/2014 12:11:20 PM


www.pdfgrip.com

viii


3.

Contents

Preparation and Properties of Non-metals
Boron
Silicon
Nitrogen (N2)
Phosphorous
Oxygen (O2)
Abnormal Behaviour of Oxygen
Sulphur (S)
Extraction
Halogens Fluorine (F2)
Chlorine
Bromine
Iodine (I2)
Allotropic Forms of Carbon
Allotropic Forms of Phosphorous
Allotropic Forms of Sulphur
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

4.

Compounds of Lighter Metals–1
Compounds of Alkali Metals

Compounds of Sodium
Sodium Chloride (NaCl)
Compounds of Potassium
General Review of Compounds of Alkaline
Earth Metals
Compounds of Calcium
Compounds of Aluminium
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

5.

3.1
3.5
3.6
3.7
3.9
3.11
3.11
3.11
3.13
3.16
3.19
3.22
3.24
3.26
3.29


4.1
4.3
4.10
4.11
4.15
4.21
4.24

Compounds of p-block Elements–1
Compounds of Boron
Compounds of Carbon
Compounds of Silicon
Compounds of Nitrogen

A01_Pearson Guide to Inorganic Chemistry_FM.indd viii

5.1
5.5
5.9
5.13

3/27/2014 12:11:20 PM


www.pdfgrip.com

Contents

Oxides of Phosphorous
Oxyacids of Phosphorous

• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

6.

6.1
6.4
6.8
6.21
6.30

Transition Elements and Co-ordination Chemistry
Transition Elements
Co-ordination Chemistry
Terms Related to Co-ordinate Complex
Preparation of Complexes
Nomenclature of Co-ordination Compounds
Isomerism in Co-ordination Compounds
Bonding in Complexes
Valence Bond Theory
Some Complexs and Their Formation
Crystal Field Theory (CFT)
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

8.


5.24
5.26

Compounds of p-block Elements–2
Ozone (O3)
Hydrogen Peroxide (Auxochrome) H2O2
Compounds of Sulphur
Oxides of Chlorine
Fluorides of Xenon
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

7.

ix

7.1
7.8
7.9
7.12
7.13
7.17
7.20
7.21
7.22
7.24


Metallurgy
Occurrence of Elements
Classification of Ores of Elements
Thermodynamic Principles of Metallurgy
Ellingham Diagram
Electrochemical Principles of Metallurgy
Unforgettable Guidelines

A01_Pearson Guide to Inorganic Chemistry_FM.indd ix

8.1
8.2
8.13
8.14
8.15
8.15

3/27/2014 12:11:20 PM


www.pdfgrip.com

x

Contents

• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions


9.

Compounds of Heavy Metals
Oxides and Chlorides of Tin
Oxides and Chlorides of Lead
Oxides
Halides
Sulphates
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questions for Self-assessment • Integer Type Questions

10.

9.1
9.4
9.7
9.9
9.12

Principles of Qualitative Analysis
Preliminary Tests
Characteristic Test of Anions (Acidic Radicals)
I Group Basic Cations
II Group Cations
III Group Cations
IV Group Cations
V Group Cation

VI Group Cation
Some Dry Tests
Unforgettable Guidelines
• Straight Objective Type Questions • Brainteasers Objective Type Questions • Multiple
Correct Answer Type Questions • Linked-Comprehensions Type Questions • Assertion and
Reasoning Questions • Matrix–Match Type Questions • The IIT–JEE Corner • Solved
Subjective Questions • Questionsfor Self-assessment • Integer Type Questions

Appendix

A01_Pearson Guide to Inorganic Chemistry_FM.indd x

10.1
10.2
10.5
10.6
10.6
10.7
10.8
10.9
10.9
10.11

A.1–A.13

3/27/2014 12:11:20 PM


www.pdfgrip.com


Preface
The Pearson Guide to Inorganic Chemistry for the JEE Advanced is an invaluable book for all the students
preparing for the prestigious engineering entrance examination. It provides class-tested course material and problems that will supplement any kind of coaching or resource the students might be using.
Because of its comprehensive and in-depth approach, it will be especially helpful for those students
who do not have enough time or money to take classroom courses.
A careful scrutiny of previous years’ IIT papers and various other competitive examinations during the last 10 to 12 years was made before writing this book. It is strictly based on the latest IIT
syllabus (2014–15) recommended by the executive board. It covers the subject in a structured way
and familiarizes students with the trends in these examinations. Not many books in the market
can stand up to this material when it comes to the strict alignment with the prescribed syllabus.
It is written in a lucid manner to assist students to understand the concepts without the help of
any guide.
The objective of this book is to provide this vast subject in a structured and useful manner so as to familiarize the candidates taking the current examinations with the current trends and types of multiplechoice questions asked.
The multiple-choice questions have been arranged in following categories: Straight Objective
Type Questions (single choice), Brainteasers Objective Type Questions (single choice), Multiple
Correct Answer Type Questions (more than one choice), Linked-Comprehension Type Questions,
Assertion and Reasoning Questions, Matrix-Match Type Questions, the IIT JEE Corner and
Integer Type.
This book is written to pass on to another generation, my fascination with descriptive inorganic
chemistry. Thus, the comments of the readers, both students and instructors, will be sincerely appreciated. Any suggestions for added or updated additional readings would also be welcome, students
can reach me directly at

Atul Singhal

A01_Pearson Guide to Inorganic Chemistry_FM.indd xi

3/27/2014 12:11:20 PM


www.pdfgrip.com


Acknowledgements
The contentment and ecstasy that accompany the successful completion of any work would remain
essentially incomplete if I fail to mention the people whose constant guidance and support has
encouraged me.
I am grateful to all my reverend teachers, especially, the late J. K. Mishra, Dr D. K. Rastogi, the
late A. K. Rastogi and my honourable guide, Dr S. K. Agarwal. Their knowledge and wisdom has
continued to assist me to present in this work.
I am thankful to my colleagues and friends, Deepak Bhatia, Er Vikas Kaushik, Er A. R. Khan,
Vipul Agarwal, Er Ankit Arora, Er Wasim, Akhilesh Pathak, Akhil Mishra, Alok Gupta, Mr Anupam
Shrivastav, Mr Rajiv Jain, Mr Ashok Kumar, Mr Sandeep Singhal, Mr Chandan Kumar, Mr P. S. Rana,
Amitabh Bhatacharya, Ashutosh Tripathi, N. C. Joshi and Rajneesh Shukla.
I am indebted to my father, B. K. Singhal, mother Usha Singhal, brothers, Amit Singhal and
Katar Singh, and sister, Ambika, who have been my motivation at every step. Their never-ending
affection has provided me with moral support and encouragement while writing this book.
Last but not the least, I wish to express my deepest gratitude to my wife Urmila and my little,
but witty beyond years, daughters Khushi and Shanvi who always supported me during my work.

Atul Singhal

A01_Pearson Guide to Inorganic Chemistry_FM.indd xii

3/27/2014 12:11:20 PM


www.pdfgrip.com

1

CHEMICAL BONDING


Chapter Contents
Orbital overlap and covalent bond; Hybridization involving s, p and d orbitals
only; Orbital energy diagrams for homonuclear diatomic species; Hydrogen bond;
Polarity in molecules; Dipole moment (qualitative aspects only); VSEPR model and
shapes of molecules (linear, angular, triangular, square planar, pyramidal, square
pyramidal, trigonal bipyramidal, tetrahedral and octahedral) and various levels
of multiple-choice questions.

CHEMICAL BOND

Attractive

Chemical bond is the force of attraction that
binds two atoms together. A chemical bond balances the force of attraction and force of repulsion at a particular distance.

Electron cloud

Repulsive
Nucleus

A chemical bond is formed to:
Fig. 1.1

attain the octet state
minimize energy
gain stability
decrease reactivity
When two atoms come close to each other,
forces of attraction and repulsion operate
between them. The distance at which the attractive forces overcome repulsive forces is called

bond distance. The potential energy for the system is lowest, hence the bond is formed.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 1

Types of Bonds
Following are the six types of chemical bonds.
They are listed in the decreasing order of their
respective bond strengths.
1.
2.
3.
4.
5.
6.

Ionic bond
Covalent bond
Coordinate bond
Metallic bond
Hydrogen bond
van der Waals bond

3/13/2014 5:23:33 PM


www.pdfgrip.com

1.2

Chapter 1


Metallic bond, hydrogen bond and van der
Waals bond are interactions.

Octet Rule
It was introduced by Lewis and Kossel.
According to this rule, each atom tries to
obtain the octet state, that is, a state with
eight valence electrons.

Exceptions to the octet rule
Transition metal ions like Cr3+, Mn2+
and Fe2+.
Pseudo inert gas configuration cations
like Zn2+ and Cd2+.

Contraction of octet state
The central atom is electron deficient or
does not have an octet state. For example,
BeX2
4

BX3
6

AIX3
6

Ge (CH3)3
6e−


Expansion of octet state
The central atom has more than 8
electrons due to empty d-orbitals. For
example, PCl5, SF6, OsF8, ICl3, etc.
S F6
P Cl5
10
12
I CI3 etc.
10 e

Os F8
16

Odd electronic species like NO, NO2
and ClO2.
Interhalogens compounds like IF7 and
BrF3.
Compounds of xenon such as XeF2, XeF4
and XeF6.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 2

IONIC OR KERNEL BOND
An ionic bond is formed by the complete transfer of valence electrons from a metal to a nonmetal. This was first studied by Kossel.
For example,
Na +
(2, 8, 1)


Cl
(2, 8, 7)

Mg +
(2, 8, 2)

O
(2, 6)

Mg+2
(2, 8)

Al + N
(2, 8, 3) (2, 5)

Al+3
N−3
(2, 8) (2, 8)

Na+
(2, 8)

C1−
(2, 8)
O−2
(2, 8)

Number of electrons transferred is equal to
electro-valency.
Maximum number of electrons transferred

by a metal to non-metal is three, as in the
case with AlF3 (Al metal transfers three electrons to F).
During electron transfer, the outermost orbit
of metal is destroyed. The remaining portion
is called core or kernel, hence this bond is also
called kernel bond.
Nature of ionic bond is electrostatic or
coloumbic force of attraction.
It is a non-directional bond.

Conditions for the Formation
of an Ionic Bond
The process of bond formation is exothermic where ΔH=−Ve. The essential conditions
include the following:
Metal must have low ionization energy.
Non-metals must have high electron affinity.
Ions must have high lattice energy.
Cation should be large with low electronegativity.
Anion must be small with high electronegativity.

3/13/2014 5:23:34 PM


www.pdfgrip.com

Chemical Bonding

Born–Haber Cycle
The formation of an ionic compound in terms
of energy can be shown by Born–Haber cycle.

It is also used to find lattice energy, ionization
energy and electron affinity.
For example,
M(s)
½ X2
+

Sublimation
+S

Decomposition
+1/2
−

M(g) + X (g)

D

M(g)

Ionization

X(g)

+I

M+(g) + e−

Addition of e−
−E


Crystal formation
−U

−

X (g)

MX(g)

ΔHf = S + 1/2 D + I − E − U
Here,
S = Heat of sublimation
D = Heat of dissociation
I = Ionization enthalpy
E = Electron gain enthalpy or electron
affinity
U = Lattice energy
For the formation of an ionic solid, energy must
be released during its formation, that is, ΔH
must be negative.
−E − U > S + ½ D + I

Properties of Ionic Compounds
1. Ionic compounds have solid crystalline
structures (flat surfaces), with definite
geometry, due to strong electrostatic force
of attraction as constituents are arranged in
a definite pattern.
2. These compounds are hard in nature.

Hardness ∝ Electrostatic
force
of
attraction
∝ Charge on ion
1
∝ ________
Ionic radius

M01_Pearson Guide to Inorganic Chemistry_C01.indd 3

1.3

3. Ionic compounds have high value of boiling point, melting point and density due
to strong electrostatic force of attraction.
Boiling point, melting point ∝
Electrostatic force of attraction
Volatile nature
1
∝ ______________________
Electrostatic force of attraction

4. Ionic compounds show isomorphism, that is,
they have same crystalline structure. For example, all alums, NaF and MgO, ZnSO4⋅7H2O
and FeSO4⋅7H2O.
5. These are conductors in fused, molten or
aqueous state due to the presence of free ions.
In solid state these are non-conductors as no
free ions are present.
6. They show fast ionic reactions as activation

energy is zero for ions.
7. They do not show space isomerism due to
non-directional nature of ionic bond.
8. They have high latice energy (U). It is
released during the formation of an ionic
solid molecule from its constituent ions.

Lattice Energy
Lattice energy is the energy needed to
break an ionic solid molecule into its constitutent ions. It is denoted by U.
U ∝ Charge on ion
1
∝ ________
Size of ion

Hence, lattice energy for the following
compounds increases in the order shown
under:
NaCl < MgCl2 < AlCl3 < SiCl4
As charge on a metal atom increases, its size
decreases.
In case of univalent and bivalent ionic compounds, lattice energy decreases as follows:

3/13/2014 5:23:34 PM


www.pdfgrip.com

1.4


Chapter 1

Bi-bi > Uni-bi or Bi-uni > Uni-uni
For example,
MgO > MgCl2 > NaCl.
Some orders of lattice energy
(i) LiX > NaX > KX > RbX > CsX
(ii) LiF > LiCl > LiI
(iii) AgF > AgCl > AgI
(iv) BeO > MgO > CaO > SrO
9. Ionic compounds are soluble in polar solvents like water due to high dielectric constant of these solvents. The force of attraction
between ions is destroyed and hence they
dissolve in the solvent.

Facts Related to Solubility
If ΔH (hydration) > Lattice energy then
the ionic compound
is soluble.
If ΔH (hydration) < Lattice energy then
the ionic compound
is insoluble
If ΔH (hydration) = Lattice energy then
the compound is at
equilibrium state

Some Solubility Orders
a. LiX < NaX < KX < RbX < CsX
b. LiOH < NaOH < KOH < RbOH <
CsOH
c. BeX2 < MgX2 < CaX2 < BaX2

d. Be(OH)2 < Mg(OH)2 < Ca(OH)2 <
Ba(OH)2
e. BeSO4 > MgSO4 > CaSO4 > SrSO4 >
BaSO4
f. AIF3 > AlCl3 > AlBr3 > AlI3
Crystals of high ionic charges are less
soluble. For example, compounds of
CO3–2, SO4–2, PO4–3 are less soluble.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 4

Compounds Ba+2, Pb+2 are insoluble as
lattice energy > ΔHhy.
Compounds of Ag (salts) are insoluble as
lattice energy > ΔHhy.
Presence of common ions decrease solubility. For example, solubility of AgCl
decreases in presence of AgNO3 or KCl,
due to the presence of common ions,
that is, Ag+ and Cl− respectively.
Note: The concept of ionic bond is not a
part of IIT-JEE syllabus but has been discussed for the better understanding of the
chapter.

COVALENT BOND
A covalent bond is formed by the equal sharing of electrons between two similar or different
atoms.
If atoms are same or their electronegativity
is same, the covalent bond between them is
non-polar. For example, X – X, O = O, N ≡ N
If atoms are different or have different value

of electronegativity, the covalent bond
formed between them is polar. For example,
+δ −δ +δ,
H − O − H,

+δ −δ
H−X

The number of electrons shared or covalent
bonds represent covalency.
One atom can share maximum three electrons
with another atom. For example, in ammonia
the covalency of nitrogen atom is three.

Properties of Covalent
Compounds
1. Covalent compounds mostly occur in liquid and gaseous state but if molecular
weight of the compound is high they may
occur in solid state too.

3/13/2014 5:23:34 PM


www.pdfgrip.com

Chemical Bonding

For example,

F2,

‘g’

Cl2
‘g’

Br2
‘l’

Glucose
Molecular wt. 180

I2
‘s’

Sugar
342

(less solid)

(more solid)

2. Solubility of these compounds follows the
concepts ‘like dissolves like’, that is, nonpolar solute dissolves in non-polar solvent.
For example, CCl4 dissolves in organic
solvents. Similarly, polar solutes dissolves
in polar solvent. For example, alcohol and
ammonia dissolve in water.
3. Covalent compounds have lower boiling
point and melting point values than those
of ionic compounds. This is because covalent bond is a weak van der Waals force in

nature.
For example,

KOH
>
Strong
ionic force
of attarction

HX
Weak
van der
Waals forces

Boiling point and melting point
∝ Hydrogen bonding
∝ Molecular weight
For example,
H2Te
H2Se
H2S
H2O,
HF > HI > HBr > HCl
Due to
As molecular
H-bonding
weight decreases
4. Covalent compounds are non-conductors
due to absence of free ions, but graphite is
a conductor, as the free electrons are available in its hexagonal sheet like structure.

In case of diamond, the structure is tetrahedral hence free electrons are not available. Therefore, it is not a conductor.
5. Covalent bond is directional, hence these
compounds can show structural and space
isomerisms.
6. The reactions involving covalent bond are
slow as these need higher activation energy.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 5

1.5

COORDINATE OR DATIVE
SEMI-POLAR BOND
Coordinate bond is a special type of bond which
is formed by donation of electron pair from the
donor to the receiver, that is, it involves partial transfer or unequal sharing of electrons. It is
denoted as (
) from donor to receiver.
A:
+
Donor or
Lewis base

B
(A
Receiver
Lewis acid

B)


Coordinate bond is intermediate between ionic
and covalent bonds, but more closely resembles
a covalent bond. The properties of coordinate
compounds are more close to covalent compounds. For example,
O
O
H +
O
H

O

H

H

F

N

B

H

F

F

H, NH4+, K4 [Fe(CN)6], N2O


Sugden Linkage
Sugden or singlet linkage is formed by donation of one electron and is denoted by ( ).
For example, PCl5, SF6, IF7.
It was studied for the first time by Lorry and
Sidwick.
Cl
Cl
Cl

F F F
S

P
Cl
Cl

F F F

Fig. 1.2

MODERN CONCEPT OF
COVALENT BOND
The nature of covalent bond is explained on the
basis of Heitler–London’s Valence bond theory,

3/13/2014 5:23:34 PM


www.pdfgrip.com


1.6

Chapter 1

Pauling and Slater’s overlapping theory and
Hund, Mullikan’s theory.

Valence Bond Theory or
Heitler–London Theory
Orbital concept of covalent bond was introduced by Heitler and London. According to this
concept, “A covalent bond is formed due to the
half-filled atomic orbitals having electrons with
opposite spin to each other”.

Features
1. The atoms should have unpaired electrons
to form a covalent bond.
2. A covalent bond is formed by the pairing
of electrons.
3. The maximum electron density lies
between the bonded atoms.
4. There is a tendency to form close shells of
the atom, though the octet is not attained
in BeCl2, BF3, etc., and is exceeded in PCl5,
SF6, IF7, etc.
Due to overlapping the potential energy of
system decreases.
The internuclear distance with maximum
overlapping and greater decrease of potential
energy is known as bond length.


Limitations
1. It cannot explain the formation of odd
electron molecule such as ClO3, NO, H2+,
etc. In such molecules, electron pairing
does not take place.
2. It cannot explain the formation of
coordinate bond where only one atom
donates a lone pair of electrons to the other
atom, molecule or ion.
3. It cannot explain the formation of π-bond.
4. It cannot explain the stereochemistry of
the molecules and ions.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 6

Pauling and Slater’s Theory
It deals with the directional nature of the bond
formed and is simply an extension of Heitler–
London theory.
1. Greater the overlapping, stronger will be
the bond formed. It means bond strength
depends upon the overlapping and is
directly proportional to the extent of
overlapping.
2. A spherically symmetrical orbit, say,
s-orbital will not show any preference in
direction whereas non-spherical orbitals,
say, p- or d-orbitals will tend to form a
bond in the direction of maximum electron

density with the orbital.

REMEMBER
The overlapping of the orbitals of only
those electrons which take part in the
bond formation will occur and not with
the electrons of other atoms.
The wave function of an electron of
s-orbital is spherically symmetrical,
therefore such an electron exhibits no
directional preference in bond formation. The two orbitals having similar
energy level, the one which is more
directionally concentrated, will form a
stronger bond.
Strongness of overlapping ∝ mode of
overlapping.
For example, linear overlapping is
stronger than lateral overlapping.
Strongness of overlapping ∝ directional
nature of orbital.
For example,
p-p > s-p > s-s > p-p
Linear or axial
Lateral
overlapping
overlapping

3/13/2014 5:23:34 PM



www.pdfgrip.com

1.7

Chemical Bonding

Types of Overlapping
1. s-s Overlapping: Overlapping between
s-s electrons of two similar or dissimilar
atoms is called s-s overlapping and forms a
single covalent bond.

it is formed by the overlapping of the 3pz
orbitals of two chlorine atoms.
Cl =1s2, 2s2 2p6, 3s2, 3px2, 3py2, 3pz1

17

−

+

+

−

p−p
Fig. 1.5

Some Important Features of Bond

s

s

Fig. 1.3 Formation of hydrogen molecule by
s-s overlapping.

2. s-p Overlapping: Overlapping between
s and p electrons is called s-p overlapping. NH3 is formed by the overlapping
between three electrons of nitrogen (px,
py and pz) with three electrons of three
hydrogen atoms.
N = 1s2, 2s2, 2px1 py1 pz1
H = 1s1
1

Bond Length
Bond length is the average distance between
the centers of the nuclei of the two bonded
atoms.
It is determined by X-ray diffraction and
spectroscopic methods.
In case of ionic compounds, it is the sum of
ionic radius of cation and anion, while in case
of covalent compounds, it is sum of their
covalent radius.

7

Strong bond can be formed only when

hydrogen electrons approach in the direction of X, Y and Z axis at right angles to
each other.

Factors affecting bond length
Bond length ∝ Size of atom. For example,
HF < HCI < HBr < HI
(Atomic size)
Since F < CI < Br < I
1
Bond length ∝ _____________________
Bond order or multiplicity
For example, C – C > C = C > C ≡ C
1.54Å 1.34Å 1.32Å

s—p
Fig. 1.4

3. p-p Overlapping: p-p overlapping is
formed by the overlapping of the p-orbitals
of the atoms. In case of chlorine molecule,

M01_Pearson Guide to Inorganic Chemistry_C01.indd 7

1
Bond length ∝ ___
s%
that is, sp3 >
s%
25%


sp2 > sp
33%
50%

Bond length ∝ Electronic repulsion
For example, H−2 > H+2

3/13/2014 5:23:35 PM


www.pdfgrip.com

1.8

Chapter 1

Resonance and hyperconjugation also
change bond length.
For example, in benzene, C – C bond length is
1.39 Å, that is, in between C – C and C=C.

Bond Energy
It is the energy needed to break one mole of
bond of a particular type, so as to separate
them into gaseous atoms. It is also called
bond dissociation energy.
Bond energy can also be defined as the energy
released during the formation of one mole of
a particular bond.


Factors affecting bond energy
Bond energy ∝ Bond order or multiplicity
For example, C ≡ C > C = C > C – C
1
Bond energy ∝ ______________________
Bond length or size of atom
For example,
HF > HCl > HBr > HI
Bond energy ∝ s% or s-orbital character
involved in hybridisation
For example,
sp, sp2, sp3
50% 33% 25%
1
Bond energy ∝ __________________
Lone pair of electrons/
electronic repulsion
For example, C − C > N − N > O − O > F − F
0
1
2
3
lp e−
B.E. (kJ) 247
163
146
138.8
Some diatomic molecules in order of bond
energy are
C=O > N≡N > C≡N > C≡C


Bond Angle
It is the angle between the lines representing
the directions of the bonds or the orbitals having bonding pair of electrons.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 8

Factors affecting bond angle
Bond angle ∝ Bond order ∝ s%
1
∝ __________
Bond length
For example,
C

C C

180°

120°

C

C

C

109°28′

Bond angle is also affected by electronic

repulsion (see VSEPR theory).
For example, NH4+ > NH3 > NH−2
no lp
1 lp e−
2 lp e−
1
Bond angle ∝ _________________
Size of terminal atom
For example, I2O > Br2O > Cl2O > OF2
Bond angle
1
∝ _____________________________
Size of central atom/electronegativity
Normally, bond angle decreases when we
move down the group, as electronegativity
decreases.
For example, NH3 > PH3 > AsH3 > BiH3
H2O > H2S > H2Se > H2Te
BF3 > PF3 > ClF3
Bond angle ∝ Electronegativity of terminal
atom
For example, PF3 > PCl3 < PBr3 < PI3
PF3 has more bond angle than PCl3 due to
pπ-dπ bonding.

REMEMBER
PF3 has greater bond angle when compared
to PH3 due to resonance in PF3, where a double bond character develops. NH3 has more
bond angle value than NF3 as F-atom pulls
the bpe– away from N-atom in NF3.


3/13/2014 5:23:35 PM


www.pdfgrip.com

Chemical Bonding

POLORIZATION AND FAJAN’S
RULE
When cation and anion are close to each other,
the shape of anion is distorted by the cation. This
is known as polarization. Due to this, covalent
nature develops in an ionic molecule.
1
Polarization ∝ Covalent nature ∝ __________
Ionic nature
+

−

Polarization

+

−

Distorted anoin
Fig. 1.6


Fajan’s Rule
Polarization or covalent nature is explained
by the following rules:
Charge on Cation Polarization, covalent
nature or polarizing power of a cation ∝
charge on cation. That is greater the charge
on cation, greater will be its polarizing
power and more will be covalent nature.
For example,
SiCl4 > AlCl3 > MgCl2 > NaCl

Size of Cation When the charge is same and
the anion is common, consider that the cova1
lent nature ∝ ___________
Size of cation
That is, smaller cation has more polarizing
power.
For example,
LiCl > NaCl > KCl > RbCl > CsCl
Max. covalent
Max. ionic
Least ionic
Least covalent
+
+
+
+
+
Li < Na < K < Rb < Cs
Smallest

Largest
in size
in size
Size of Anion This property is taken into
account when the charges are same and
the cation is common.

M01_Pearson Guide to Inorganic Chemistry_C01.indd 9

1.9

Polarization or covalent nature ∝ size
of anion. Hence, larger anions are more
polarized.
For example, LiF < LiCl < LiBr > LiI
Since, F− < Cl− < Br− < I−
Larger the size of anion, easier will be its
polarization.
A cation with 18 valence electrons has
more polarizing power than a cation
with 8 valence electrons.
For example,
Group IB > Group IA
Cu+
Na+
Αg+
K+
Group IIB > Group IIA
Zn+2
Mg+2

For example,
ZnO > MgO
Zn+2
Mg+2
2, 8, 18 2, 8

REMEMBER
As the covalent nature increases, the intensity of the colour increases. For example,
FeCl3 is reddish-brown while FeCl2 is
greenish-yellow.

Dipole Moment
+q

–q

r

Fig. 1.7

3/13/2014 5:23:35 PM


www.pdfgrip.com

1.10

Chapter 1

Dipole moment is used to measure the polarity

in a molecule. It is denoted by μ. Mathematically, it is given as
μ = q × r coulomb metre
μ = e × d esu cm
1 debye = 1 × 10−18 esu cm.
It is represented by (
) from electropositive to electronegative species or less
electronegative to more electronegative species. For example, AX3

OR

NH2

X

F

X

X

OH

X

Homoatomic molecules like X2, N2, O2 and
molecules having normal shapes according
to hybridization like linear, trigonal, tetrahedral will be non-polar, as for them, the
dipole moment is zero. For example, BX3,
CH4, CCl4, SiCl4, PCl5.


X
A
X

X
μ=0
Non-polar
μ1
θ
μ2

In case of para forms M μnet is positive if both
the species are different. For example,

μ=0

μres.
O

In case a molecule has more than one polar
bonds μnet is given as follows:
Dipole moment ∝ Electronegativity difference. For example, HF > HCI > HBr > HI
Dipole moment ∝ Number of lone pair of
electrons.
For example, HF > H2O > NH3
Fluorine has 3 lone pair, oxygen has 2 lone
pair, and ammonia has 1 lone pair of electron.
1
Dipole moment ∝ __
θ

ortho > meta > para
For example,
X

X

X

X

‘o’

‘m’

X
‘p’

60°

120°

180°

M01_Pearson Guide to Inorganic Chemistry_C01.indd 10

B
F
F
μnet = 0


O

F

C ×
×
×
μnet = 0

F
Xe

F

F
μnet = 0

Here, μ (net) = 0 as C = O bonds are in
opposing directions.
Molecules in which the central atom has
lone pair of electrons or have distorted
shapes, like angular, pyramidal, sea-saw
shapes will have some value of dipole
moment and will be polar in nature. For
example, H2O, H2S, OF2, NH3, PH3, PCl3,
SCl4, SO2, SnCl2 etc.
μ(net) = 1.82D

>
X


>

C

×

__________________

μnet= √μ12+μ22 +2μ1,μ 2 Cos θ

F

O
H

H

3/13/2014 5:23:35 PM


www.pdfgrip.com

1.11

Chemical Bonding

μ (net) = 1.47D

N


μ (net) = 1.03D

>

H

N
F

H

H

Ammonia has more dipole moment than NF3
as in ammonia μ (net) is in the direction of lone
pair electrons i.e., it is additive while in NF3 μ
(net) is opposite to lone pair i.e., substractive.
Dipole moment of a cis-alkene is more than
trans-alkene. In trans-alkenes, it is zero due
to symmetry in most of the cases.

F

F

Dipole Moment of Some Common Molecules
Molecule H2 N2 CH4 Cl2 CS2 C2H2 CH2F2 O2

Dipole

0
moment

0

0

0

0

0

O3

1.96D 0 0.52D

C2H6 SO2

0

CO Csl NaCl CH3OH C2H5OH H2O HF

1.61D 1.12 12.1 8.3

Molecule HCl NH3 N2O H2S H2O2 NF3 CHCl3 PH3 HCN SbCl3 CH3Cl S8 PCl5

Dipole
1.02 1.46 0.17 0.92 1.84 0.55 1.15 0.58 2.93 3.9
moment


H

C

CH3

H

H C CH3
cis-but-2-ene

C

CH3

CH3 C H
trans-but-2-ene

Exception: Unsymmetric alkenes with odd
number of carbon atoms have some value of
dipole moment.
For example, trans-2-pentene
CH3

0

0

0


1.67D 1.84 1.91

Trans
but-2ene

IF7

0

0

PX5 CX4

0

0

Uses
To find geometry of a complex/molecule etc.
To find ionic character or nature in a covalent
species.
μobserved
Ionic nature % = ____________
× 100
μcalculated (q × r )
To distinguish between −cis and −trans
alkenes
Cis-but 2-ene > trans but-2-ene
μ=+ve

μ=0

H
C=C

H

1.86

1.69

CH2CH3

Illustrations
Specific cases of dipole moment
→ CH3Cl > CH2Cl2 > CHCl3 > CCl4
Highly polar

Non-polar

→ CH3Cl > CH3F > CH3Br > CH3I

M01_Pearson Guide to Inorganic Chemistry_C01.indd 11

1. The experimentally determined dipole
moment of KF is 2.87 × 10−29 cm. The distance between the centers of charge in a KF
dipole is 2.66 × 10−10 m. Calculate the percentage ionic character of KF.

3/13/2014 5:23:36 PM



www.pdfgrip.com

1.12

Chapter 1

Solution
μ = e × d coulombs meter

Sigma(σ) bond

For KF = 2.66 × 10−10 m
For complete separation of a unit charge (electronic charge), e = 1.602 × 10−19 C
μ = 1.602 × 10−19 × 2.66 × 10−10
= 4.26 × 10−29 cm
% of ionic character of a KCl
2.87 × 10−29
× 100
4.26 × 10−29
= 67.4%.
2. The dipole moment of KCl is 3.336 × 10−29
coulomb meter which indicates that it is
a highly polar molecule. The interatomic
distance between K+ and Cl− in this molecule is 2.6 × 10−10 m. Calculate the dipole
moment of KCl molecule if there were
opposite charges of one fundamental unit
located at each nucleus. Calculate the percentage ionic character of KCl.
=


Solution
μ = e × d coulombs meter
For KCl d = 2.6 × 10−10 m
For complete separation of unit charge (electronic charge), e = 1.602 × 10−19 C
μ = 1.602 × 10−19 × 2.6 × 10−10
= 4.1652 × 10−29 cm
μ (KCl) = 3.336 x 10−29 cm
Per cent ionic character of KCl
3.336 × 10−29 × 100
= ____________
4.1652 × 10−29
= 80.09%

S–S

σ bond
P

S

σ bond
P

P

Fig. 1.8

1. Sigma bond is stronger and therefore less
reactive, due to more effective and stronger
overlapping than σ bond.

2. The minimum and maximum number of
σ bonds between two bonded atoms is 1.
3. Stability ∝ Number of sigma bonds.
1
4. Reactivity ∝ __
σ
5. In sigma bond, free rotation of the atoms
is possible.
6. Sigma bond determines the shape of
molecules.

Pi (π) Bond
Pi bond is formed by lateral or sidewise overlapping between the two p orbitals.
π bond
+

+

−

−

Fig. 1.9

Sigma (σ) Bond

1. It is a weak or less stable bond, and therefore more reactive, due to less effective
overlapping.
2. Minimum and maximum number of π
bonds between two bonded atoms are 0

and 2, respectively.
1
3. Stability ∝ ________________
.
Number of π bonds

Sigma bond is formed by axial or headtohead or
linear overlapping between two s – s or s – p or
p – p orbitals.

4. Reactivity ∝ Number of π bonds.
5. In case of a π bond, free rotation is not
possible.

SIGMA AND PI BONDS

M01_Pearson Guide to Inorganic Chemistry_C01.indd 12

3/13/2014 5:23:36 PM