The document provides an introduction to chemical bonding, including definitions of key terms like chemical bond, ionic bond, covalent bond, and coordinate bond. It describes the three main types of bonds: ionic formed by electron transfer, covalent formed by electron sharing, and coordinate bonds formed when one atom provides both electrons. Examples of bond formation are given for ionic compounds like NaCl and MgCl2 and covalent compounds like Cl2, CO2, and NH3. Characteristics of ionic and covalent compounds are also summarized.

1. Prepared by:
Keyur Maradiya
EXCELLENCE CLASSES
CHEMICAL BONDING

2. Introduction
EXCELLENCE CLASSES
 It is a universal rule that everything in this world tires to
become stable by attaining the lowest state of energy. The
stability of atoms is stable electronic configurations. It leads to
reactivity. The inert gases are chemically inactive, so their
electronic configurations are stable. All atoms have a tendency
to react due to the presence of incomplete valence shell. They
combine to attain the inert gas electronic configuration.
 Atoms tend to combine chemically involving distribution of
electrons in such a manner that each atom is left with a stable
electronic configuration. During this process, a force of
attraction develops between the atoms which binds them
together to form molecules. This force is called chemical
bond.

3. EXCELLENCE CLASSES
 Defn of Chemical Bond – It is an attractive force
which holds the constitutent atoms together in a
molecule. A molecule is an elecrically neutral cluster
of mutually bonded atoms.
 CAUSES OF CHEMICAL COMBINATION
1. Tendency to acquire noble gas configuration (Kossel and Lewis)
Law of Octet - Elements having 8 electrons in their valance shell are
chemically less reactive and hence extremely stable.
Law of Duplet – Elements having 2 electrons in their valence shell i.e
K shell are found to be stable.
2. Tendency to acquire state of minimum energy :
Atoms of various elements combine with each other only if chemical
combination leads to decrease in energy. If on combination the energy
of the system increases , no bond is said to be formed be formed
between them.

4. Types of Chemical Bonds
EXCELLENCE CLASSES
 There are three ways in which atoms attain stable
configuration through chemical combination:
 By electron transfer - Electrovalent
 Electron sharing - Covalent
 Electron sharing in which both the electrons are supplied for
sharing is provided by the only one atom and not by both
atoms. – Coordinate or Dative bond

5. EXCELLENCE CLASSES

6. Electrovalent (Ionic ) Bond
EXCELLENCE CLASSES
 Defn of Electrovalent Bond -A combination or bond formed by the
complete transfer on one or more electrons from the atom of one element
to the atom of another element is called an ionic or electrovalent bond.
 For example, in the formation of a molecule of sodium chloride, an ionic
bond is formed between the atoms of sodium and chlorine.
 Cation – Atom which loose electron is said to be electropositive and the
ion formed by it is known as cation.
 Anion – Atom which gain electron is said to be electronegative and the
ion formed by it is known as anion.
 Defn of Electrovalency – It is the number of electrons lost or
gained by an atom of the element to acquire stable configuration
during the formation of electrovalent bond.
 e.g Mg - Atomic no. 12 – Config (2,8,2) – looses 2 electrons hence
electrovalency -2

7. Formation of Sodium Chloride
EXCELLENCE CLASSES
Sodium (Na) Chlorine (Cl)
Atomic No. 11 17
Ele. Configuration 2,8,1 2,8,7

8. Formation of Magnesium Chloride
EXCELLENCE CLASSES
Magnesium (Mg) Chlorine (Cl)
Atomic No. 12 17
Ele. Configuration 2,8,2 2,8,7

9. Formation of Calcium Oxide
EXCELLENCE CLASSES
Calcium (Ca) Oxygen (O)
Atomic No. 20 8
Ele. Configuration 2,8,8,2 2,6

10. Conditions favouring formation of
ionic bond
EXCELLENCE CLASSES
 Electronegativity Difference - Greater the electronegativity
difference between the two combining atoms , stronger is the bond
formed .
 Ionisation Energy- The ionisation energy is the amount of energy,
which is required to remove the most loosely bound electron(s)
from an isolated gaseous atom to form a positive ion.
During formation of an ionic bond, one atom must form a cation by
losing one or more electrons. In general, elements having low
ionisation energies have a more favourable chance to form a cation,
thereby having a greater tendency to form ionic bonds. Thus, the
lower ionization energy of metallic elements favours the formation
of an ionic bond.

11. EXCELLENCE CLASSES
 Electron affinity - It is the amount of energy released when an
isolated gaseous atom accepts an electron to form a negative ion.
The other atom participating in the formation of an ionic compound
must form an anion by gaining an electron (s). Higher electron
affinity favours the formation of an anion. Therefore, generally, the
elements having higher electron affinity favour the formation of an
ionic bond.
 High Lattice Energy - It is the measure of the energy contained in
the crystal lattice of a compound, equal to the energy that would be
released if the component ions were brought together from infinity.

12. Characteristics of Ionic Compound
EXCELLENCE CLASSES
 Physical state of ionic compounds - Due to the presence of the
strong force of attraction between the positive and negative ions,
ionic compounds are solids and are hard to break. They generally
break into pieces when pressure is applied, hence they are considered
brittle.
 Melting and boiling points - Due to the presence of electrostatic
forces of attraction between ions, a large amount of energy is required
to break the ionic bonds between the atoms. Thus, ionic compounds
have high melting and boiling points.
 The solubility of ionic compounds - Ionic compounds are generally
soluble in polar solvents such as water whereas solubility tends to
decrease in non-polar solvents such as petrol, gasoline, etc.

13. EXCELLENCE CLASSES
Conduction of Electricity - Ionic compounds do not conduct
electricity in the solid-state but are good conductors in a molten state.
Conduction of electricity involves the flow of charge from one point
to another. In the solid-state, as the movement of ions is not possible,
ionic compounds don’t conduct electricity. Whereas in the molten
state, ionic compounds conduct electricity as electrostatic forces of
attraction between the ions are overcome by the heat released.

14. Covalent Bond
EXCELLENCE CLASSES
 Defn of Covalent Bond –The chemical bond formed by
the sharing of electrons in order to achieve noble gas
configuration is known as covalent bond.
 Covalent bond is always formed between two non metals
as they have 4 -7 valance electrons .
 Defn of Covalency – It is the number of electrons shared
during the formation of covalent compound is known as
covalency.
 e.g Chlorine(Cl2) - Atomic no. 17 – Config (2,8,7) –
Shares 1 pair of electrons hence covalency – 1.

15. Types of Covalent Bond
EXCELLENCE CLASSES
 Single Covalent bond
 Double Covalent bond
• Triple Covalent bond
 Formation of Single Covalent Bond – It is sharing formed by sharing of
one electron pair between two atoms in which each atom contributes
one electron.

16. EXCELLENCE CLASSES
 Formation of Double Covalent Bond – It is sharing formed by
sharing of two electron pair between two atoms in which each
atom contributes two electron.
 Formation of Three Covalent Bond – It is sharing formed by
sharing of three electron pair between two atoms in which each
atom contributes three electron.

17. EXCELLENCE CLASSES
 Formation of Chlorine Molecule
Atomic No Electronic Config
Chlorine 17 2,8,7

18. EXCELLENCE CLASSES
 Formation of Carbon Tetrachloride Molecule
Atomic No Configuration
Carbon 6 2,4
Chlorine 17 2,8,7

19. EXCELLENCE CLASSES
 Formation of Carbon Dioxide Molecule
Atomic No Configuration
Carbon 6 2,4
Oxygen 8 2,6

20. EXCELLENCE CLASSES
 Formation of Nitrogen Molecule
Atomic No Electronic Config
Nitrogen 7 2,5

21. Non- Polar & Polar Covalent Molecules
Excellence Classes
Covalent Molecules
Non – Polar
molecules Polar Molecules

22. Excellence Classes
 Non – Polar Covalent Molecules – A covalent bond
between two similar or dissimilar atoms which have zero
or small electronegativity difference is called non –polar
covalent bond and the molecule so formed is called as
non-polar molecule.
 E.g For similar atoms - Hydrogen, Chlorine , Oxygen.
For dissimilar atoms - Methane , Carbon tetrachloride.
In case of methane the shared pair of electrons are at equal
distances from the carbon and hydrogen atoms because the two
atoms (C & H ) have nearly same electronegativities ( C- 2.5 & H
– 2.1)

23. Excellence Classes
 Polar (puller) Covalent Molecules – If a covalent bond is
formed between the atoms having different electronegativities
the shared pair of electrons is not at equal distances from
two atoms and the combining atoms acquire partial positive
and partial negative charge such a covalent bond is called
polar covalent bond and such a molecule is called polar
molecule.
 E.g. – HCl , H2O, NH3 etc.

24. Excellence Classes
Non –polar compounds Polar - compounds
1. Non polar compounds do not
have any charge seperation
1. Polar compounds contain
charge seperation
2. Insoluble in water but soluble
in organic solvents
2. Soluble in water but insoluble
in organic solvents
3. Bad conductors of electricity 4. Good conductors of electricity
in aqueous solution.
4. Non polar bonds are usually
formed between two identical
atoms
4. Polar bonds are usually formed
between two different atoms

25. Characteristics of Covalent
compounds
EXCELLENCE CLASSES
 Covalent compounds usually have low melting points. An exception
to this include molecules of silica and diamonds that have a high
melting point.
 These compounds have low boiling points. This can be attributed to
their weak force of attraction between the various bonded atoms.
Van Der Waals forces bind these atoms.
 These compounds are usually gases and liquids with low boiling and
melting points.
 These compounds are non-conductors of electrical charge. The
absence of charged ions is the main reason behind this.
 They are bad conductors of heat also. Their molecules lack free
electrons and that obstructs the flow of heat energy.
 Covalent compounds are generally insoluble in water and other
polar solvents but soluble in organic solvents like benzene and
toulene, etc.

26. Coordinate Bond
EXCELLENCE CLASSES
 Bond Pair – A pair of electrons shared between two atoms is called
bond pair of electrons.
 Lone Pair – A pair of electrons present on an atom which is not
shared with another atom is called lone pair.
 Coordinate Bond – The bond formed by sharing of electrons
between two atoms in which both the electrons of the shared pair
are contributed by one of the atoms where as the other atom simply
takes part in sharing is called coordinate or dative bond.
 Conditions favouring formation of Dative bond
 1. One of the two atoms must have its octet complete having atleast
one lone pair of electrons in its valence shell.
 2. Another atom must be short of two electrons in its valance shell.
 E.g. Ammonium Ion (NH4
+) & Hydronium ion (H3O+)

27. Formation of Ammonium Ion (NH4
+)
EXCELLENCE CLASSES
Atomic No Electronic Config.
Nitrogen 7 2,5
Hydrogen 1 1

28. Formation of Hydronium Ion (H3O+)
EXCELLENCE CLASSES
Atomic No Electronic Config.
Oxygen 8 2,6
Hydrogen 1 1

29. Oxydation and Reduction
Excellence Classes
 Oxidising agents – It is one that oxidises other substances by
gaining one or more electrons or providing oxygen or an
electronegative ion or by removing hydrogen or an
electropositive ion .
 Eg. Oxygen, Chlorine Hydrogen peroxide ,etc
 Reducing agents – It is one that reduces other substances by
giving one or more electrons or by giving hydrogen or an
electropositive ion or by removing oxygen or an
electronegative ion .
 E.g Hydrogen, Carbon, Ammonia ,etc.
 Redox Reaction – A reaction in which oxidation and reduction
take place simultaneously is called redox reaction.
 Eg . Zn + Cu2+  Zn2+ + Cu

30. Excellence Classes
 Here Zn looses 2 electrons so it undergoes oxidation.
 Cu gains two electrons so it undergoes reduction.
 Reducing agent – Zn (as it looses two electrons)
 Oxidising agent – Cu ( as it gains two electrons)