The document explains various types of chemical bonds, including ionic, covalent, and coordinate covalent bonds, detailing their characteristics and formation examples. It discusses the limitations of the octet rule, resonance, dipole moments, and properties of different types of molecular solids. Additionally, it explores hydrogen bonds and metallic bonds, along with the effects of these bonds on the physical state and solubility of compounds.

1. Chemical Bonding and Shape of Molecules
Chemical Bond: The force of attraction which binds the atoms, ions or molecules
together is called chemical bond.
Valence shell: The outermost shell of an atom is called valance shell.
Valence electron: The electrons in outermost shell of an atom is called valance
electrons.
Lewis symbols: The outer shell electrons are shown as dots(or cross) surrounding
the symbol of the atom. These symbols are known as Lewis symbols.
The concept of Lewis symbols was introduced by G. N. Lewis

2. Lewis Dot Symbols for 1-20 elements

3. Octet rule :
The tendency of the atoms to acquire eight electrons in their outermost shell by
gaining, losing or sharing of electrons is known as octet rule.
Limitation of octet rule :
• Octet rule is violated for the compounds containing hydrogen atom. Eg. H2O,
NH3, H2SO4 etc.
• It could not explain the formation electron deficient molecules such as BeCl2,
BF3, AlCl3 etc.
• It could not explain about the excess electron of phosphorus atom in PCl5,
SF6, IF7 etc.

4. Types of chemical bond :
Electrovalent bond or ionic bond:
The bond formed by the complete transfer of electron from one combining atom to
the valence shell of another combining atom is called electrovalent bond.
The no. of electrons lost or gained during the formation of electrovalent bond is
termed as electrovalency of the element.
This type of bond is formed when the combining atoms have large difference in
electronegativity. The compound formed through ionic bond is called
electrovalent or ionic compound.

5. Characteristics of ionic compound:
Ionic compound have following characteristics.
1. Ionic compound are generally crystalline in nature.
2. They are soluble in water and other polar solvent but insoluble in non polar
solvent like benzene.
3. Ionic compound do not conduct the electricity at solid state. However, They are
able to conduct the electricity in the molten state or in aqueous solution.
4. They are hard but brittle in nature.
5. Ionic compound have high melting and boiling point. Since electrovalent bond is
very strong bond so large amount of heat is required to break the bond.
6. The density of ionic compound is higher due to the presence of strong
electrostatic force of attraction between the cations and anions.

6. Eg. of ionic compounds:
NaCl, CaF2, MgS, Na2S, MgCl2, CaO, etc.
Formation of ionic compound (Lewis symbols) :
i) Formation of sodium chloride
NaCl is formed by complete transfer of one electron from valence shell of sodium
to valence shell of chlorine.
Na× + ̇Cl̤̈꞉ Na+ + Cl-
(2,8,1) (2,8,7) (2,8) (2,8,8)
[Na+][Cl-]

7. Covalent Bond:
The bond formed by mutual sharing of one or more valance electrons between the
combining atoms of same or different elements having similar electronegativity is
called covalent bond. The number of electron shared by an atom during the
formation of covalent bond is called covalency . The compounds formed by
formation of covalent bond are called covalent compounds. e.g. CH4, C2H6, H2O
etc.
Characteristics of covalent compound:
The covalent compound have following characteristics.
1. Covalent compound exist in solid, liquid and gaseous state.
2. They have low melting and boiling point value and are insoluble in water but
soluble in nonpolar solvent, Like benzene.

8. 3. They do not conduct the electricity.
4. The reaction of covalent compounds are slow than that of ionic compound.
Eg. of covalent compounds:
H2, O2, N2, H2O, CH4, HF, H2S, HCN,C2H2,NH3, CH3OH, CCl4, H2O2,
CO2,CHCl3.
Lewis structure of some covalent compound:
i) Formation of H2 molecule
Hydrogen molecule is formed by sharing of one-one electron of each atom of
hydrogen in which both atoms form their duplet.
H× + ×H H2

9. Coordinate Covalent Bond Or Dative Bond:
The bond formed when one-sided sharing of electron pair takes place is called a
coordinate covalent bond. Such bond is known as dative bond. The atom which
provides the electron pair is termed as the donor atom while the other atom which
accept it is termed as acceptor. A coordinate covalent bond is represented by an
arrow (→) pointing towards the acceptor atom. The resulting compounds are
known as coordinate covalent compound.
Characteristics of Coordinate Covalent Compound :
1. They are generally exist in liquid and gaseous state.
2. They are sparingly soluble in water and organic solvent due to semi ionic in
nature.
3. The melting point and boiling point of coordinate covalent compound is lower
than covalent compound .

10. Lewis structures of some coordinate covalent compounds:
i) Formation of O3 ii) Formation of N2O
O = O → O N ≡ N → O
iii) Formation of SO2 iv) Formation of CO
O = S → O O = C
v) Formation of SO3 vi) Formation of N2O4
O O O
↑ ↑ ↑
O = S → O O = N – N = O
vii) Formation of P2O5 viii) Formation of HNO3
O O O
↑ ↑ ↑
O = P – O – P = O H - O – N =O

11. ix) Formation of H2SO4 x) Formation H3PO4
O O
↑ ↑
H – O – S – O – H H – O – P – O – H
↓ │
O O – H
xi) Formation of HClO (Hypochlorus acid)
H – Cl → O
xii) Formation of H2SO3 (Sulphurous acid)
O
↑
H – O – S – O – H O
xiii) Formation of H2CO3 ‖
(Carbonic acid) H – O – C – O – H

12. 14) Formation of HNO2 (Nitrous acid)
O
↑
H – N = O
15) Formation of H3O+
H
|
H – O → H+
16) Formation of SO4-- O
↑
-O – S – O-
↓
O

13. 17) Formation of fluoroborate ion (BF4
-)
F
│
F – B ← F-
│
F
18) Formation of NH4Cl
H
│
[ H – N → H+] + Cl-
│
H

14. Hydrogen Bond :
When hydrogen atom is bonded with highly electronegative element such as F, O,
N then the shared pair of electron lies more towards the electronegative element.
Hence partial positive and negative charge generate i.e. molecule becomes polar.
The bond between the hydrogen atom of one molecule and a more
electronegative atom of the same or another molecule is called hydrogen bond.
It is shown by dotted line (……….) .
Condition for formation of hydrogen bond:
1. The element link with hydrogen atom in molecule should be highly negative
(Like F,O,N).
2. The atom of the highly electronegative element should be small.

15. Types of Hydrogen Bond :
Intermolecular hydrogen bond :
The hydrogen bonding between the H- atom of one molecule and an atom of
electronegative element of another molecule is called intermolecular hydrogen
bond. For example hydrogen bonding in water, ammonia etc.
H – O ……H – O……..H – O ….. H – O
| | | |
H H H H
Intramolecular hydrogen bond :
The hydrogen bonding between the hydrogen atom and more electronegative
atom within the molecule is called intramolecular hydrogen bond. For example
hydrogen bonding in o- nitrophenol, salicylic acid etc.

16. Application of hydrogen bond:
i) Solubility of covalent compound : covalent compound generally insoluble
in water. However the covalent compound which can form the hydrogen
bond with water readily dissolve in it.
ii) Physical state: Hydrogen bonding affects the physical state of a substance.
For example H2O is liquid while H2S gas at room temperature.
iii) Increase in melting and boiling point : Stronger the hydrogen bonding
greater will be the intermolecular force of attraction so large amount of heat
is required for breaking the bond. Thus m.p. and b.p. of hydrogen bonded
compound becomes high.

17. Metallic Bond :
Metallic bond appears in metal and some alloys. The
bonding in metal was first explained by Drude and
Lorentz. According to them metal consist of
positively charged metallic ions (kernal) and valence
electrons are moving between the ions like gas
molecule. so this is also called electron sea model.
The simultaneous force of attraction between the
mobile electron and positive charged ion which
binds the metal atoms together is known as
metallic bond.
In metal, valence electrons are not completely bound
and they are mobile. Due to this, metals are good
conductor of electricity.

18. Metals have following specific properties,
which are due to metallic bond:
a) Metals are good conductor of electricity.
b) Metals are malleable and ductile.
c) Metals have lustre.
In metallic crystal, there are free electrons.
The free electrons allow a current to flow
through metallic crystals. When a negative
charge is applied at one end, it moves
towards the other end. So, Metals are good
conductor of electricity.
Due to metallic bonding, metal
atoms have ability to shift into
new positions without breaking
the bond. If a small stress is put
onto the metal, the layers of atoms
will start to roll over each other. It
is the reason for malleability and
ductility of metals.
The outermost electrons in
metals can move freely in
the metal causing any light
incident on them to get
reflected back. Due to this
reflection, metal surface
appears shiny or lustrous.

19. Vander Waal’s force of attraction :
Dutch chemist Vander waal Proposed that there is a force of attraction between
the non-polar molecule. This force is called Vander waal force. It can be
imaginated that due to rapid movement of electron, the electron distribution of
atom may be unsymmetrical with slight increase in electron density in one side
which develops the positive and negative end at a particular instant. i.e. a
temporary dipole is formed. Such dipole is called instantaneous dipole and which
develops the induced dipole to another atom near to it.
The attractive forces between the instantaneous dipoles and induced dipoles
are called Vander Waal forces or London forces.

20. Classification of crystalline solid:
Crystalline solids are classified on the basis of nature of bonding which are given
as:
i) Ionic Solid :
The solid in which the crystals are formed from ions and they are held together
in crystal lattice by strong electrostatic force of attraction is called ionic solid.
They have high melting and boiling point and conduct the electricity in
aqueous solution. e.g. NaCl, KCl, CaCl2 etc.
ii) Metallic Solid :
The solids in which structural units are metal atom and they are bonded with
each other by metallic bond are called metallic solid. They are good conductor
of electricity. e.g. iron, silver, copper etc.
iii) Molecular solids :
The solids in which structural unit are molecules and

21. molecules in crystal lattice are held together by very weak Vander waal force are
called molecular solids. e.g. iodine, camphor, solid carbon dioxide etc.
iv) Covalent Solids :
The solid in which structural units are atoms and they are combined together by
covalent bond between them are called covalent solids. e.g. diamond, graphite
etc.
Resonance :
There are some molecules which can represented by more then one lewis
structure due to delocalization of non bonded electrons or pie- electrons. Such
lewis structure are called resonating structure and phenomenon is called
resonance. In other word resonance can be defined as the electronic effect which
is arises due to delocalization of pie electron.

22. The actual structure is regarded as a combination of these
various structures which is called resonance hybrid and it is the most stable form.
Resonating structure of some molecules :
i) Ozone (O3)
[ O = O → O ↔ O ← O = O] ≡ O – O – O
ii) Sulphur trioxide (SO3)
O O O O
↑ ‖ ↑ │
[O ← S = O ↔ O←S→O ↔ O = S→O] ≡ O – S – O
iii) Sulphur dioxide (SO2)
[O = S → O ↔ O ← S = O] ≡ O – S – O

23. iv) Carbonate ion (CO3
- -)
O- O O- O
│ ‖ │ │
[O = C – O- ↔ -O – C – O- ↔ -O – C = O] ≡ [O – C – O]2-
v) Nitrate ion (NO3
- )
O O- O O
↑ | ‖ |
[O = N – O- ↔ O ← N = O ↔ -O – N → O] ≡ [O –N –O]-
Bond Length:
Bond length is defined as the average distance between the centers of nuclei of the
two bonded atoms in a molecule.

24. Partial ionic characters of covalent compounds :
When the covalent bond is formed between two different atoms then the bonding
pair of electron are not lie exactly midway between the two atoms. The electron
attracting tendency of the atoms in a molecule is describe in terms of
electronegativity. More electronegative atom attract the electron pair toward itself,
Which bears the partial negative and partial positive charge on the atoms. As the
difference in electronegativity is increased the covalent bond becomes ionic.
Polar Covalent Bond :
The covalent bond formed between two different atoms having different
electronegativity is called polar covalent bond. The compound formed by such types
of bond are called polar covalent compounds. E.g. HCl, HBr, H2O etc.

25. Non-polar covalent bond :
The covalent bond formed between two atoms having same electronegativity then
electron pair is equally pulled by both atom as a result polarity is not produced.
Such type of bond is called non-polar covalent bond. The compound formed by
such type of bond are called non-polar covalent compounds. e.g. molecule like
H2,N2, Cl2 etc.
Dipole moment :
The ionic character in a covalent molecule is expressed in terms of dipole moment.
It is defined as the product of magnitude of charge on any one of atoms and
distance between them. It is denoted by ‘μ’ and given by
μ = q × d
Where, q = The magnitude of either charge
d = The distance between positive and negative charge

26. It is a vector quantity and is represented by an arrow pointing from positive centre
to negative centre.
The unit of dipole moment is Debye (D)
1 D = 1 × 10 -18 esu × cm = 1 × 10 -10 A˚
For polyatomic molecule, the total dipole moment is calculated by taking the vector
sum of dipole moment along different atoms with respect to centre atom, which
helps to explain the geometry and polarity of molecule. If the net dipole moment of
polyatomic molecule is zero then the molecule becomes non polar and has regular
geometry and if the net dipole moment of polyatomic molecule is non zero then
molecule becomes polar and has irregular geometry.

27. Application of dipole moment:
1. It determine the ionic character of covalent molecule.
2. It helps to determine the polarity and non-polarity of the molecule.
3. It helps to explain the geometry of some molecules.
CO2, CS2, HgX2 etc. ( zero dipole moment value) has linear where as H2O, H2S,
SO2, N2O, BF2 etc.(non-zero dipole moment) has bent structure.
Q1. Why water has a bent structure whereas carbon dioxide has linear structure?
Q2. Carbon oxygen bond is polar in CO2 but it is non polar molecule. Why?