Chemical bonds are the forces that hold atoms together in molecules and crystals. There are two main types of bonds: ionic and covalent. Ionic bonds involve a complete transfer of electrons between atoms, giving one atom a positive charge and the other a negative charge. Covalent bonds involve sharing of electron pairs between atoms. Covalent bonding can involve single, double or triple bonds with one, two or three shared pairs respectively. Ionic compounds are usually solids with high melting points, while covalent compounds have lower melting points due to weaker intermolecular forces.

1. CHEMICAL
BONDING
Chapter # 05
Class 9
Prepared by Saliha Rais

2. CHEMICAL BOND
The forces which holds atoms
together in a molecule or a crystal is
called a Chemical Bond

3. TYPES OF CHEMICAL BONDS
 There are two major types of bonds:
1. Ionic or Electrovalent Bond.
2. Covalent Bond.

4. IONIC BONDS

5. IONIC OR ELECTROVALENT
BOND
 Complete transfer of electron from one
atom to another.
 The atom that transfers electron gets
positive charge.
 The atom that gains electrons gets
negative charge.
 The strong electrostatic force acting
between positive and negative ions holds
them together.

6. DEFINITION
“The attraction that binds oppositely
charged ions together is termed
electrovalent bond, or ionic bond.”

7. EXAMPLE
Sodium atom
transfers one outer
most shell electron
and become
positive sodium
ion, and chlorine
atom gains that
electron to
complete its
outermost
shell(octet) and
become chloride
negative ion.

8. CHARACTERSTICS OF IONIC
COMPOUNDS
1. In the crystals of ionic compounds the
oppositely charged ions are mutually
surrounded by each other in orderly
arrangement. Thus ionic compounds are
solids at room temperature.

9. 2. Ionic
compounds have
high melting and
boiling points
because of
strong
electrovalent
bonds existing
between the ions.

10. 3. Ionic solids do not
conduct electricity,
as the ions are not
free to move. Once
an ionic compound
is melted (fused) the
ions are free to
move and conduct
electricity. Similarly,
Solutions of ionic
compounds
conduct electricity.

11. 4. Ionic compounds are usually soluble in
polar solvents, i.e. solvents of high
dielectric constant, such as water. But
they are insoluble in non-polar, organic
solvents. These solvents have low
dielectric constant value, such as
benzene, carbon tetrachloride, etc.
They are mostly inorganic compounds.

13. CAN YOU GUESS….!
 When two same elements combine, does
the electrons transfer?
 When two different elements having
same electronegativity reacts, does the
electron transfer occur?

14. When two or more atoms of the same
element, or atoms of different
elements having same
electronegativity react, the transfer
of electron does not occur.

15.  The atoms complete there outermost
shells by sharing unpaired electrons, and
a covalent bond is formed.
 In covalent bond each atom has to
contribute equal number of unpaired
electrons.

16. DEFINITION
“The shared pair of electrons which
links the atoms in a molecule is
known as covalent bond.”

17.  The bond is expressed by a single short
line.

18. TYPES OF COVALENT BONDS
 There are three types of covalent bond.
1. Single covalent bond
2. Double covalent bond
3. Triple covalent bond.

19. 1. SINGLE COVALENT BOND:
 Only one pair of electrons is shared by the
boned atoms.
 Each atom has to share one electron.
 It is represented by single short line (----)

20. 2. DOUBLE COVALENT BOND:
 Two pairs of electrons are shared by the
bonded atoms.
 Each atom has to share two unpaired
electrons.
 It is represented by two short lines.

21. 3. TRIPLE COVALENT BOND:
 Three pairs of electrons are shared
between the bonded atoms.
 Each atom has to share 3 unbounded
electrons.
 It is denoted by three short lines.

22. CHARACTERSTICS OF
COVALENT COMPOUNDS.
1. Compounds with covalent bonds are
usually made up of discrete units with a
weak intermolecular force.

23. 2. In the solid state there are weak Vander
Wall forces between the molecules.
Hence covalent compounds are often
gases, liquids or soft solids with low melting
points.

24. 3. They are insulators because they do not
conduct electricity.
4. Covalent compounds are usually
insoluble in polar solvents like water, but
soluble in organic solvents like benzene,
ether, etc.

25. ELECTRONEGATIVITY IN
COVALENT COMPOUNDS.
 If a covalent bond
is formed between
two like atoms, the
molecule is called
non-polar,
because the
electron pair is
shared equally
between two same
atoms.

26.  However if the
covalent bon is
formed between
two dissimilar
atoms, the
attraction for
electron pair would
not be equal. One
atom will attract
the shared pair
more towards itself.

27. ELECTRONEGATIVITY
“The power of an atom to attract
the shared pair of electrons
towards itself, is known as
electronegativity.”

28. IONIC CHARACTER IN
COVALENT BOND:
1. NON-POLAR COVALENT BONDS
2. POLAR COVALENT BONDS
3. ELECTROVALENT BONDS

29. 1. NON-POLAR COVALENT BONDS
 It is the covalent
bond between two
like atoms
 The molecule will be
electrically neutral as
well as symmetrical.
 The difference in the
electronegativities of
the bonded atoms
will be zero.

30. 2. POLAR COVALENT BONDS:
 It is the covalent bond
formed between two
dissimilar atoms.
 The shared pair of
electron will move closer
to more electronegative
atom.
 There will be partial
positive and partial
negative charges on the
atoms.
 The difference of
electronegativities is up to
1.7.
 These molecules are
partially ionic in
character.

31. 3. ELECTROVALENT BONDS:
 When the
difference in the
electronegativities
of bonded atoms is
more than 1.7,
than the bond is
purely ionic or
electrovalent.
 The participating
atoms will bear a +
or – charge.