2. 2
CHEMICAL BONDS
1. Valence electrons
2. Electron dot structures
3. Molecules and Ions
4. Formation of Ions
5. Ionic bonds and Ionic compounds
6. Covalent bonds and molecular compounds
7. Coordinate Covalent bonds
8. Bond polarity
9. Attraction between molecules
10. Shapes of molecules
3. 3
Chemical Bonding
Classification
Intramoleculr bonding
Force of attraction
within the molecule
determine
Chemical properties
Ionic Bonds
between ions
Force of attraction
between two or
more molecules
determine
Physical properties
i. Dipole-Dipole attraction
ii. Hydrogen Bonding
iii.London Forces
Intermolecular bonding
Bonds are formed
Bonds are formed
Covalent Bonds
between Nonmetals
Nonpolar Polar
5. 5
I- Intramolecular Chemical
I- Intramolecular Chemical
Bonding
Bonding
Intramolecular chemical bonding refers to the
attractive forces that holds the atoms
together to form a molecule
H2, O2, CH4 NaCl, MgCl2 etc.
Major classes
I) Ionic bonds
II) Covalent bonds
6. 6
Because All atoms would like to attain (reach) stable
electron configurations like noble gases
by:
losing electrons
or sharing electrons
or gaining electrons.
For a stable configuration each atom must fill its
outer energy level:
1st
: 2 electrons
2nd
: 8 electrons
3rd
: 8 electrons
4th
: 8 electrons
Reason for Intramolecular Chemical Bonding
7. 7
Valence Electrons
The electrons in outer shell are called valence
electrons. These electrons are very influential
(important) as they determine chemical
properties of the elements.
For representative elements, the number of
valence electrons in an atom is equal to the
group number.
Li C S
Group
Number
6A
IA 4A
9. 9
Group Number and Arrangement of Valence Electrons
Group Selected Electron Number of Electron-Dot
Number Elements Arrangement Valence Electrons Structure
1A Li 2-1 1
2A Ca 2-8-2 2
3A Al 2-8-3 3
4A C 2-4 4
5A N 2-5 5
6A S 2-8-6 6
7A Cl 2-8-7 7
8A Ne 2-8 8
Li
Ca
Al
C
N
S
Cl
Ne
11. 11
Types of intramolecular Bonding
I-Ionic Bonding
Ionic bonds are formed due to the transfer of
electrons from one atom (metal) to another atom
(nonmetal) to give oppositely charged particles called
ions to attain a noble gas arrangement.
Electrically charged atoms or groups of
atoms are called ions. They are very
reactive species
H+
, Li+
, OH-
, Br-
etc
12. 12
Types of ions
1- Positive Ions (Cations)
Positively charged ions: H+, Na+, K+, Ca+
They are formed by loss of an electron
(size of cation is smaller than atom BECAUSE A
CATION LOSES A SHELL).
2-Negative Ions ( Anions )
Negatively charged ions: Cl- , OH- , I-
They are formed by gain of an electron
(size of anion is bigger than corresponding atom
because entering electron and electrons already
present, repel each other and shell get enlarged).
13. 13
To form an ion, an element has to lose or gain
electrons and form stable full outer shell of a noble
gas
Electronic configuration of lithium, carbon and fluorine
Atomic number 3
Lithium
Electronic configuration
2,1
Atomic number 6
Carbon
Electronic configuration
2,4
Atomic number 9
Fluorine
Electronic configuration
2,7
Which elements form ions?
Many non metals
can gain electrons
to form negatively
charged ions
Some non metals
with partly filled
electrons shell
do not form ions
All metals can
lose electrons
to form positively
charged ions
14. 14
IA IIA IIIA IVA VA VIA VIIA
Li+
Be2+
C4-
N3-
O2-
F-
Na+
Mg2
Al3+
Si4-
P3-
S2-
Cl-
K+
Ca2+
Se2-
Br-
Rb+
Sr2+
Te2-
I-
Cs+
Ba2+
Group Number
Ions formed by the representative elements
+
15. 15
A positive ion produced by loss
of one or more electrons from metal atom.
Li+
, Na+
,K+
, Mg2+,
Ca2+
, Al3+
, etc.
Anion
A negative ion formed by gain
of one or more electrons by non metal.
F1-
,Cl1-
, O2-
, N3-
, C4-
etc
X
c Charge
Element
Ions formed by the Representative Elements
Cation
16. 16
Ionic bonds are formed between a metal and a
non-metal.
Bonding occurs using valence electrons.
Ionic Bonding and Octet Rule
•Atoms that have 5, 6 or 7 electrons in their outer
levels will tend to gain electrons from atoms with
1, 2 or 3 electrons in their outer levels
•Atoms that have 1, 2 or 3 electrons in their outer
levels will tend to lose them in interactions with
atoms that have 5, 6 or 7 electrons in their outer
levels.
•Atoms try to get 8 electrons in the
valence shell (octet rule)
17. 17
Formation of sodium chloride or common
salt
•Na atom looses an electron and forms Na+ ion.
•Cl atom gains an electron and forms Cl- ion.
NaCl
(Ionic compound)
Oppositely Charged ions, Na+
and Cl-
attract each other and
form ionic compound, NaCl.
Cl
+
Na
+ -
Cl
-
Na
+
Na Na+
cations
anions
+ e
+ e
Cl
-
Cl
18. 18
Ionic Giant Molecule of NaCl
Ionic Giant Molecule
Cl
Cl
Cl
Na
Na
Na
Cl
Na
Na
Cl
Na
Cl
Cl
Cl
Na
Cl
Na
Cl
Cl
Na
Cl
Na
Na
Cl
Na
Na
Na
Cl
Cl
Na
Cl
Na
Na
Cl
Cl
Na
Cl
Cl
Cl
Na
Cl
Na
Cl
Na
Na
Cl
Na
Cl
Na
Na
Na
Cl
Na
Cl
Cl
Na
Cl
Cl
Cl
Na
Na
Na
Cl
+
Atoms A Atoms B
Many atoms
Electrons transfered
from atoms A to atoms B
Na Cl
•Ionic bond is the attraction between cations and anions
•Na+
and Cl-
ions are stacked together
•Lowest energy arrangement
•The pattern is repeated throughout the crystal or Lattice
Cl
19. 19
Loses 2e-
Each gains 1e-
One
Magnesium ion
Mg2+ Two
Chloride ions
2Cl-
Magnesium and Chloride ions Combine to
form MgCl2 (Magnesium chloride)
Formation of Magnesium chloride
MgCl2
Mg Mg2+
Cl
Cl
Cl
Cl
20. 20
Lewis structure
• Lewis symbols help us to find the valence
electrons and predicts bond
Na. + :Cl.
..
.. Na+ :Cl:
..
..
-
Mg 2:Cl.
..
.. Mg :Cl:
..
..
-
2+
2
.
. +
Magnesium chloride
Sodium chloride
21. 21
PROPERTIES OF IONIC COMPOUND
a. They have high melting and boiling points due to
presence of strong intermolecular force of
attraction.
b. They are non-volatile: they do not easily turn into
gas.
c. Generally soluble in water because they generally
ionize in water.
d. Solids do not conduct electricity because the ions
are held together by strong electrostatic force of
attraction.
e. Conduct electricity when melted.
f. Aqueous solution conducts electricity because the
ions are mobile in solutions.
g. They are generally insoluble in organic solvents,
because organic solvents are covalent compounds.
22. 22
The noble gases are known for their chemical stability
and existence as mono atomic molecules as they contain
8 electrons in outer most shell
(valence shell) except Helium
Nobel gases He Ne Ar Kr Xe Rn
Valence electrons 2 8 8 8 8 8
Period no. 1 2 3 4 5 6
No. of shells 1 2 3 4 5 6
Other atoms also want electronic configurations just
like noble gases (concept of duplet & octet rules) due to
their Stability so they form ionic bond
Why Ionic Bond are Formed?
Reasons
1.Stability of noble Gases
23. 23
Li
1
1
H
2
3
He
C
6
12
4
7
Be B C N O F Ne
4 5 6 7 8 9 10
9 11 12 16
14 19 20
Na Mg Al Si P S Cl Ar
11 12 13 14 15 16 17 18
23 24 27 28 31 32 35.5 40
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
19 20 21 2223 24 25 26 27 28 29 35 36
30 31 32 33 34
39 40 45 48 51 52 55 56
Rb Sr Y Zr NbMo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg Ti Pb Bi Po At Rn
Fr Ra Lr Rf Db Sg Bh Hs MtUunUuuUub UutUuq Uuh
IA
IIB
IIIB IVB VIB
VB VIIB VIIIB IB
IIA IIIA IVA VA VIA VIIA
VIIIA
1
2
3
4
5
6
7
84
59 59 63.5 65 70 73 75 79 80
38 39 40
37 41 42 43 44 46
45 47 48 49 50 51 52 53 54
La Ce Pr NdPm Sm Eu Gd Tb Dy Ho ErTm Yb
Ac Th Pa U Np PuAmCm Bk Cy EsFm Md No
55 56
57 58 59 60 61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
87
89
88
90 91 92 93 94 95 96 97 98 99 101
100 102
103 104 105 106 107 108 109 110 111 112 113 114 116
85.5 88 89 91 93 96 (98) 101 103 106 108 112 115 119 122 131
133 137
128 127
175 178.5 181 184 186 190 192 195 197 201 204 207 209 (209) (210) (222)
(223) 226 (260) (261) (262) (263) (262) (265) (266) (269) (272) (277) (289) (289)
138 140 141 144 (145) 150 152 157 159 162.5 165 167 169 173
227 232 231 238 237 (244) (243) (247) (247) (251) (252) (257) (258) (259)
NON METAL
C
H
Hg
SOLID
GAS
LIQUID
METAL
METALLOID
PERIODIC TABLE OF ELEMENTS
25. 25
Simple Binary (double) Compounds of Metals and a Nonmetals
Simple Binary (double) Compounds of Metals and a Nonmetals
• One element is metal and the other is a non-metal
• The metal (+ve) is name first, followed by
the nonmetal (-ve)
• Only two different elements are present
• Number of each is given as a subscript
• Overall formula must have no Charge
Examples:
metal nonmetal
NaCl Sodium chloride
SrO Strontium oxide
Al2S3 Aluminum sulfide
Binary compounds= Compound composed of two different
elements
In ionic compounds one is metal and the other is non-
metal.
26. 26
Naming ionic compounds
IUPAC Methods of Naming
• Firstly, Name the cation (metal)
• When an element has only one charged state
• Secondly, Name the anion (nonmetal) using the ending (-ide)
• Examples
CrCl3 Chromic chloride,
MgBr2 Magnesium bromide,
Al2O3 Aluminum oxide,
K3N Potassium nitride,
MgS Magnesium sulfide
Ca2C Calcium carbide
SrO Strontium oxide
27. 27
Formula for some ionic compounds
NaCl MgCl2 AlCl3
Na2O MgO Al2O3
Na3N Mg3N2 AlN
Some simple ions
Cations Na+
Mg2+
Al3+
Anions Cl-
O2-
N3-
Simple short cut can be used to obtain the formula of an
ionic compound by exchanging superscript for subscript
Naming of Ionic Compounds
Ca 2 +
Ca3(PO4)2
PO4
3 -
Al 3 O 2
Al 2O 3
-
+
28. 28
Naming ionic compounds
B group metals may have more than one possible
charge ( due to more than one oxidation state).
Use roman numerals (I,II,III) in the name to indicate
the charge on the metal.
.
Cu1+
+ O2-
= Cu2O
copper (I) oxide copper (I) oxide
Cu2+
+ O2-
= CuO
copper (II) oxide copper (II) oxide
29. 29
Naming ionic compounds
FeBr3
Each bromide is 1-
so iron 3+
FeBr3 Iron (iii) bromide
FeCl2 iron (ii) chloride
FeCl3 iron (iii) chloride
SnBr2 tin (ii) bromide
SnBr4 tin (iv) bromide
AgCl silver chloride
CdS cadmium sulfide
There are some exception
Some B metals only have a single
state so the roman numeral may be omitted
Some A metals have more than one
State so numbers must be used
30. 30
Some ions have characteristic colors they impart to
their compounds as seen below
Solution of
potassium
chromate,
which contains the
yellow chromate
ion,CrO4
2-
.
Polyatomic ions
Solution of
potassium
permanganate, which
contains the violet
permanganate Ion,
MnO4
-
Solution
of potassium
dichromate
ion, Cr2O7
2-
.
A poly atomic ion is a group of nonmetal atoms (which are
covalently bonded together), that carries electrical
charge
31. 31
Some common polyatomic ions
Cation Name of cation Anion Name of anion
NH4+ ammonium ClO2
-
chlorite
H3O+ hydronium ClO-
or OCl-
hypochlorite
PO4
3-
phosphate
HPO4
2-
hydrogen phosphate
H2PO4-
dihydrogen phosphate
CrO4
2-
chromate
Cr2O7
2-
dichromate
MnO4- permanganate
CH3CO2- acetate
NO3- nitrate
OH- hydroxide
O2
2-
peroxide
SO4
2-
sulphate
32. 32
AgNO3 silver nitrate
H2O2 hydrogen peroxide
Fe2(SO4)3 iron (III) sulphate
Naming compounds containing polyatomic ions
Most polyatomic ions have names that end with -ate or- ide.
NH4Cl ammonium chloride
NaOH sodium hydroxide
KMnO4 potassium permanganate
(NH4)2SO4 ammonium sulfate
Write the positive ion, first, and then write the name
of the polyatomic ion
33. 33
Chemical Formulas of complex compounds
Example: Copper sulfate CuSO4.5H2O
CuSO4.5H2O.
Blue crystal
CuSO4
White powder
heat
35. 35
Bonds are formed between two non metals by
sharing of one or more pairs of electrons.
CH4
, CCl4, O2
, H2, H2O, HCl, HF ,
NH3, CO2
COVALENT BONDS
The attractive forces between two atoms
dominate (take over) the repulsive forces.
Total potential energy decreases
as a result
bond is formed at a short distance,
called bond distance.
36. 36
P P P
P
P P
P P
e-
e-
e-
e-
e-
e-
e-
e-
D Combination of forces
A
No interaction
B Attraction begins
C Covalent bond
+ +
+ +
+
+
+
+
Formation of covalent bond
Formation of covalent bond
Both nuclei repel each other,
as both electron clouds do
The nucleus of one atom attracts the
electron clouds of the other atom ,
vice versa electron share
37. 37
Formation of Covalent Bond
Example: Formation of ICl Molecule
Atom B
+
Two atoms
Electron pair shared
Between atom A and
Atom B
Atom A Atom B
Atom A
Chlorine
+
Two atoms
Electron pair shared
between iodine and
Iodine chlorine
Iodine Chlorine
38. 38
C H
H
H
H
1. H.
+ .
H H :H or HH
2. H.
+ .
F H : F or HF
Or
4H. H:C:H
:
:
H
H
3. + C
methane
H2
HF
CH4
Examples
Electron-Dots
Structures
Molecular Models
39. 39
x x
x
x
x
x
x
x
x x
x
x
x
x
x
x
Cl x x
x
x
x
x
x
x
x x
x
x
x
x
Cl
x
x
Cl2 molecule
a shared
electron
pair forms a
single
covalent bond
Other ways of showing a chlorine molecule:
Other ways showing a hydrogen chloride molecule:
H-Cl
HCl molecule
x x
x
x
x
x
x
x
x x
x
x
x
x
Cl
x
x
x
x
H
Covalent Compounds
Cl-Cl
40. 40
x x
x
x
x
x
x
x
x
x
x
x x
O O
x
x
An oxygen molecule
two shared electrons pairs
form a double covalent bond
double bond
A nitrogen molecule
Other ways of showing a nitrogen molecule
x
x
x
x
x
x
x
x x
x
x
N
x
x N
x
three shared electrons pairs
form a triple covalent bond
triple bond
Other ways of showing an oxygen molecule
Multiple Covalent Compounds
41. 41
Lewis Structure
H H
Two electrons Two electrons
When two hydrogen atoms share a pair of
electron the covalent bond is formed.
1. H• + H • → H••H
H H
H
H
C
C + 4H
2.
42. 42
More Examples of Lewis Structure
H N H
H
H F H
H
O
O O
C O C O
Eight electrons
O C O
Multiple Covalent Bonds
Covalent Bonds
43. 43
COORDINATE COVALENT BONDS
• The type of bond, in which a pair of electrons
from one atom is shared by two atoms, is called
a coordinate covalent bond.
Example
The reaction of boron tri-chloride, BCl3, and
ammonia, NH3.
H N:
H
H
+ B Cl
Cl
Cl
H N
H
H
Cl
Cl
Cl
B
: H N
H
H
Cl
Cl
Cl
B
Coordinate covalent bond.
44. 44
PROPERTIES OF COVALENT
COMPOUNDS
a. Low melting and boiling points because of weak
intermolecular binding force
b. They are generally volatile because of their low M.P.
and B.P.
c. They are mostly insoluble in water
d. Even if some covalent compounds dissolve in water they
do not form ion and remain almost undissociated.
e. They are generally soluble in organic solvents.
f. They are non-conductors of electricity in solid state.
45. 45
Polarity of molecules
Electrons in a covalent bond rarely get shared
equally. Unequal sharing results in polar bonds
H F
Slight positive side Slight negative side
Smaller electro negativity Larger electro negativity
Polar covalent bonds
Electrons may not be shared equally.
This is based on the electro-negativity difference
between the two elements forming the bond.
If:
1.Electronegativity difference > 1.7 (ionic bond)
2.Electronegativity difference = 0 (covalent non-polar
bond)
3.Values between 0 and 1.7 are polar covalent bond –
In polar covalent electrons are not shared equally
47. 47
Shapes of Molecules
Electron Dot Bonded Molecular
Molecule Structure Atoms Shape (angle)
CH4
4 tetrahedral (1090
)
NH3
3 pyramidal (1090
)
H2
O 2 bent (1090
)
H H
H
H
C
H N H
H
H
H
O
BCl3 3
Cl
B
Cl
Cl
planar-trigonal
48. 48
Molecular Geometry
Molecules have specific shapes which is
determined by the number of electron
pairs around the central species.
An electron group can be the electron pairs
bonded to atoms or a lone pair.
Geometry affects factors like polarity and
Solubility.
Multiple bonds are treated as a single bond for
geometry
49. 49
Characteristic physical properties
Boiling point
The temperature at which a liquid is converted
to a gas at atmospheric pressure.
Melting point
The temperature at which a solid is converted
to a liquid.
Compounds Bond Mp Bp
N2 nonpolar -210 -196
O2 nonpolar -219 -183
NH3 polar -78 -33
H2O polar 0 100
NaCl ionic 804 ?
51. 51
Forces between Molecules that determine
Physical properties
Intermolecular Attractions
Types of Intermolecular Attractions
1 Dipole – dipole attractions
2. Hydrogen Bonding
3. London Forces
52. 52
These attractions are weaker than ionic or covalent
bonds (i.e. only 1% strong).
These attraction are due to the electrons which make
the bond but
are not equally shared between atoms
because of a difference in electro-negativity
of these atoms.
δ+ and δ- ends are attracted to each other .
δ+ δ- δ+ δ- δ+ δ-
1- Dipole–Dipole Attractions
53. 53
2. Hydrogen Bonding
(dipole-dipole interaction)
The attraction between a hydrogen atom in
one molecule and an electronegative atom
(F,O,N) in another molecule is hydrogen bonding
Hδ+
—Fδ-
…… Hδ+
—Fδ-
…… Hδ+
—Fδ-
This attraction is responsible for high boiling
point of water
55. 55
Water Ice
The density of ice is 0.931 gm/cubic cm.
This compares with a density of 1.00 gm/cubic cm.
for water so ice floats on water
H
H
H
O
O
O
O
O
H
H
H
H
H
H
H
In liquid water each molecule is hydrogen bonded to approximately 3- 4
other water molecules
In ice each molecule is tetrahedrally hydrogen bonded to 4 other
molecules. which controls the orientation such that ice has empty
spaces which makes ice lighter
Tetrahedral shape
Density of Ice
56. 56
3.London Dispersion Forces
Van der Waal forces
The attraction of positively charged nucleus of one
atom for electron cloud of an atom in nearby
molecule.
These are relatively weak forces and
exist in symmetrical non-polar molecules like
CH4, SO3, CO2, O2, H2, He
Random motion of electrons for instant causes
electrons more on one side & instantaneous dipole
is produced that induces a dipole in its neighbor.
57. 57
London forces
As the dipole forms in atom A,
it induces a dipole in atom B
London forces are momentary and called
instantaneous dipole
A B
δ-
δ+ δ+ δ-
58. 58
The electron density fluctuates in two neighboring atoms,
giving rise to fleeting attractions between the
momentary dipoles.
δ+ δ−
δ−
δ+
δ− δ+
δ− δ+
δ+ δ−
Flickering On and Off of the Dipoles
No Polarization
Instantaneous
Dipoles on atom A induces a dipole on
atom B
A B A B
59. 59
Exercise
CHEMICAL BONDING
M.C.Q: Choose the best answer.
1. Force of attraction that holds atoms in a
molecule together is:
a) covalent bond b) ionic bond
c) chemical bond d) coordinate bond
2. If atoms gain or lose electron, they will
form:
a) ions b) cations
c) anions d) Polar covalent bond
3. Indicate the members of nonmetals:
a) Lithium b) Oxygen
c) Chlorine d) both b & c
60. 60
M.C.Q
4. The formation of ions from neutral atoms is nearly always:
a) endothermic b) exothermic
c) both a & b. d) none of the above
5. In making bonds atoms obey octet rule, so number of electrons in
their outer shell may be:
a) 2 or 8 electrons b) 6 or 8 electrons
c) 8 or 10 electrons d)18-electrons
6. Choose the polar compound:
a) CH4 b) NaCl c) HCl d) Both a & c
7. The bond formed in CH4 molecule is by:
a) Loss of electrons b) Gain of electrons
c) Sharing of electrons d) Both a & b
61. 61
8. The loss of electron/electrons from outer shell of
metals make them:
a) positive ion and smaller in size than corresponding atom
b) negative ion and smaller than atom
c) positive ion and bigger than atom
9. Gain of electron/electrons by non metals changes them into:
a) positive ions b) negative ions
c) neutral atoms d) both a & b
10. Example of anion:
a) K+
b) O- 2
c) Mg +2
d) Na
11. Ionic compounds:
a). HF b) Ca O C) H2O d). Both a & b
62. 62
12. If difference between electro negativity values of the atoms is
> 1.7 they will form:
a) Ionic bond b) Covalent bond
c) Polar covalent bond d) Non polar covalent bond
13. The force of attraction among water, H2O ,molecules
is:
a) Dipole-dipole interaction b) London forces
c) Hydrogen bonding d) None of the above.
14The molecule that shows London dispersion forces is:
a) NaCl b) CO2 c) H2O d) MgO
15. What are Intermolecular Forces?
a) Hydrogen bonding b) London Forces
c) Dipole-dipole interaction d) All of these
63. 63
16. The atoms complete their outer shells by obeying octet rule
and
attain electronic configuration of:
a) Alkali metals b) Halogens c) noble gases d) Transition
metals
17. Energy required to break a chemical bond & form a neutral
isolated atom is called:
a) Bond energy b) Bond order
c) Bond distance d) both a & b
18. Find out the chemical formula of organic solvent named carbon
tetra chloride:
a) :CCl2 b) CH4 c) CCl4 d) CHCl3
19. Identify the ionic molecule:
a) NH3 b) N2 c) H2O d) NaCl
