1
BASICS OF CHEMISTRY
01. SYMBOL OF THE ELEMENTS:
۞ A chemical symbol is a shorthand method of representing an element.
۞ The elements in the Periodic Table are written in their chemical
symbols. The chemical symbol is always written with a capital letter.
Sometimes a second small letter is used.
۞ Quite a number elements associated with symbols derived from their
Greek or Latin name.
۞ Some symbols are derived from their English name and some elements
are named after the name of scientists, cities etc.
۞
Examples:
i)
Symbols of the elements derived from their English names:
Name of the element
Oxygen
Atomic number of the
element
8
Symbol of the
element
O
Magnesium
12
Mg
Silicon
14
Si
Chlorine
17
Cl
2
ii)
iii)
Symbols of the elements derived from their Latin names:
Name of the
element
Sodium
Atomic number
of the element
11
Latin name of
the element
Natrium
Symbol of the
element
Na
Potassium
19
Kalium
K
Iron
26
Ferrum
Fe
Copper
29
Cuprum
Cu
Silver
47
Argentum
Ag
Lead
80
Plumbum
Pb
Symbols of the elements derived from the name of scientists:
Name of the
scientist
Name of the
element
Atomic
number of the
element
Symbol of the
element
Pierre Curie
and
Marie Curie
Curium
92
Cm
Albert Einstein
Einsteinium
99
Es
Enrico Fermi
Fermium
100
Fm
Dmitri
Ivanovich
Mendeleev
Mendelevium
101
Md
Niels Bohr
Bohrium
107
Bh
Wilhelm
Roentgen
Roentgenium
111
Rg
3
02. ATOMIC STRUCTURE:
i)
What is an atom?

An atom is a smallest particle of an element that uniquely defines
a chemical element.
ii)
What are atoms made up of?

An atom consists of a central nucleus that is usually surrounded by
one or more electrons. Each electron is negatively charged. The
nucleus is positively charged and contains one or more relatively
heavy particles known as protons and neutrons. Electrons, Protons
and Neutrons are known as sub atomic particles.
iii)
Protons, neutron & electrons.

These particles have the following properties:
iv)

Particle
Charge
Mass
Proton
+1
1
Neutron
0
1
Electron
-1
Negligible
The important points to keep in mind are as follows:
Protons and neutrons have almost the same mass, while the
electron is approximately 2000 times lighter.

Protons and electrons carry charges of equal magnitude, but
opposite charge. Neutrons carry no charge (they are neutral).
v)
In an atom :

Protons and neutrons are tightly packed together in the centre of
the atom forming the nucleus of the atom. Protons and neutrons
are collectively known as nucleons. Electrons move rapidly around
the nucleus.
4

Atoms are electrically neutral. An atom contains an equal
number of positively charged protons and negatively charged
electrons. The positive and negative electric charge cancels out
exactly.
vi)
Atomic number/Proton number:

The number of protons in an atom is called the atomic number or
proton number of the element.

Proton number is the identity of an element.
vii)
Nucleon number/Mass number:

The total number of protons and neutrons in an atom of an
element is known as nucleon number or mass number.
viii)
Isotopic notation:
 Example of Isotopic notation:

Number of particles in a neutral atom:
۞
Proton number
=6
۞
Atomic number
=6
۞
Electron number
=6
۞
Nucleon number
= 12
۞
Mass number
= 12
۞
Neutron number
= (12 – 6)
=6
5
ix)
Forming ions:

An ion is a charged particle formed from an atom or a
group of atoms by the loss or gain of electrons.
In an ion the number of protons is different from the

number of electrons.
Atoms of metals tend to lose valence electrons to form

positive ions or cations. In this way, they achieve a noble
gas structure.
Atoms of non-metals tend to gain electrons to form

negative ions or anions. In this way, they achieve a noble
gas structure.
x)

If the particle is an ion?
For a cation (positively charged ion):
۞ Proton number
= 12
۞ Atomic number
= 12
۞ Electron number = (12 – 2)
= 10
۞ Nucleon number = 24
۞ Mass number
= 24
۞ Neutron number = (24 - 12)
= 12
6
xi)
For an anion (negatively charged ion):
۞
Proton number
=7
۞
Atomic number
=7
۞
Electron number
= (7 + 1)
=8
۞
Nucleon number
= 14
۞
Mass number
= 14
۞
Neutron number
= (14 - 7)
=7
xii)
Why a neutral atom has no charge?

In a magnesium atom:
۞
Proton number
۞
Electron number = 12
۞
Charge on 12 protons
= 12
= + 12
Charge on 12 electrons = - 12
۞
Overall charge = 0
7
xiii)
Why a cation has positive charge?
۞
In a beryllium ion:
۞
Proton number
۞
Electron number = (4 - 2)
=4
=2
۞
Charge on 4 protons
=+4
Charge on 2 electrons = - 2
۞
xiv)
Overall charge
= +2
Why an anion has negative charge?
۞
In a chloride ion:
۞
Proton number
= 17
۞ Electron number = (17 + 1)
= 18
۞ Charge on 17 protons
= + 17
Charge on 18 electrons = - 18
۞ Overall charge
= -1
8
xv)
What does an atom look like?
۞ Protons and neutrons are held together rather closely in the
center of the atom. Together they make up the nucleus,
which accounts for nearly all of the mass of the
atom.
۞
Electrons move rapidly around the nucleus and constitute
almost the entire volume of the atom.
xvi)
Isotopes:

Isotopes are atoms of the same elements with the same
number of protons but different number of neutrons.


Similarities:
i)
Same number of protons
ii)
Same number of electrons.
Dissimilarities:
i)

Different number of neutrons
Chemical property:
Isotopes have the same chemical property because they
have same electronic configuration.

Physical property:
Isotopes have the different physical property because
they have different relative masses.

Examples:
9
Hydrogen
Deuterium
Tritium
Proton number
1
1
1
Electron number
1
1
1
Nucleon number
1
1
1
Neutron number
(1-1)=0
(2-1)=1
(3-1)=2

Chlorine has two isotopes, chlorine 35 and chlorine 37.
۞
Carbon has three isotopes, carbon 12, carbon 13, carbon 14.
۞
Bromine has two isotopes, bromine 79, bromine 81.
۞
Number of particles in each isotope?

Calculation of relative atomic mass of chlorine:
۞
How?
۞
Relative abundance (% of availability) of ۞
Chlorine 35 is 75% and Chlorine 37 is 25%.
(35x75) + (37x25)
۞
Relative atomic mass = ---------------------------100
= 35.5

Calculation of relative atomic mass of bromine:
۞
Abundances ?
۞
Relative abundance (% of availability) of
Bromine 79 is 50% and Bromine 81 is 50%.
۞
Relative atomic mass of bromine?
۞
Is it 80 ? That’s good.
10
xvii)
۞
What is electronic configuration?
The electronic configuration is the distribution of electrons of
an atom in shells.
۞
The shell that is furthest from the nucleus is called the outer
shell or the valence shell.
۞
The electrons in the valence shell are called valence electrons
or valency electrons.
۞
The chemical properties of an element depend on the number of
valence electrons.

۞
Number of electrons in a shell:
Formula to calculate number of electrons in a shell = 2n2
Where, n = Shell number 1,2,3,4 etc.
۞

Hence, shell # 1 can accommodate (2x12 ) =
2 electrons
shell # 2 can accommodate (2x22 ) =
8 electrons
shell # 3 can accommodate (2x32 ) =
18 electrons
But there is an exception.
Up to Calcium (atomic number 20), shell number 3 can
accommodate only 8 electrons.
11
 Electronic configuration of first 20 elements:
Element
Symbol
Electronic
configuration
Atomic
number
,
Hydrogen
H
1
1
Helium
He
2
2
Lithium
Li
3
2,1
Beryllium
Be
4
2,2
Boron
B
5
2,3
Carbon
C
6
2,4
Nitrogen
N
7
2,5
Oxygen
O
8
2,6
Fluorine
F
9
2,7
Neon
Ne
10
2,8
Sodium
Na
11
2,8,1
Magnesium
Mg
12
2,8,2
Aluminium
Al
13
2,8,3
Silicon
Si
14
2,8,4
Phosphorus
P
15
2,8,5
Sulfur
S
16
2,8,6
Chlorine
Cl
17
2,8,7
Argon
Ar
18
2,8,8
Potassium
K
19
2,8,8,1
Calcium
Ca
20
2,8,8,2
12
xviii) Position of the element in the periodic table:
۞
From the electronic configuration of an element, we can
easily find out the position of the element in the Periodic Table.
۞
How ?
Number of shell(s) = Period number
Number of electron(s) in the outermost shell = Group number
۞
Example:
Calcium (atomic number 20)
The electronic configuration is 2,8,8,2
Hence, the position of Calcium in the Periodic Table is
Period number = 4
Group number = 2
xix) Valency: It is the combining power of an element.
۞
How to find out ?
۞
For metals,
Valency = Group number
۞
For non metals,
Valency = (8 – Group number)
۞
Example:
Magnesium is a metal and it is in Group 2
So, valency of magnesium is 2.
Nitrogen is a non metal and it is in Group 5
So, valency of nitrogen is (8 – 5) = 3.
13
xx) Group Number and Ionic Charge:
۞
Every element has a tendency to attain the electronic configuration
of the nearby noble gas either by donating or by accepting
(sometimes sharing) electrons.
۞
Number of electrons transferred or shared is equal to their
valency.
۞
۞
Metal donates electron(s) to form a cation (positively charged ion).
Non metal gains electron(s) to form an anion (negatively charged
ion).
 For metals, number of positive charges on the ion is equal to their
valency . i.e. equal to their Group number.
 For non metals, number of negative charges on the ion is equal to
their valency . i.e. equal to their (8 – Group number) = Valency
.
14
xxi)
SUMMARY:
Number of particles:
Proton number
= 17
Atomic number
= 17
Mass number
= 35
Nucleon number
= 35
Neutron number
= (35-17) = 18
Electron number
= 17
Electronic configuration
= 2, 8, 7
Group number
=7
Period number
=3
Metal/Non-metal
= Non-metal
Valency
= (8 – 7) = 1
Ionic charge
= -1
Number of electron gained = 1
Cation/Anion
= Anion
15
03. ACIDS AND BASES:
 Acids:
An acid is a substance which produces hydrogen ions as only
positively charged ions when dissolved in water. E.g. HCl,
HNO3, H2SO4.

Physical properties of acids:
i)
Acids turn damp blue litmus paper red.
ii)
Acids are sour in taste and soapy feel.
iii)
Acids have a pH less than 7.
iv)

Acids are corrosive.
Chemical properties of acids:
i)
Acids react with reactive metal to form salt and
hydrogen gas.
Mg(s) + 2HCl(aq)
ii)
→
MgCl2 (aq)
+
H2(g)
Acids react with a metal hydroxide to form salt and
water.
HCl(aq) + NaOH(aq) → NaCl(aq) +
iii)
Acids react with a metal oxide to form salt and water.
CuO(s) + H2SO4 (aq) → CuSO4 (aq)
iv)
H2O(l)
+
H2O(l)
Acids react with a metal carbonate to form salt,
carbon dioxide and water.
2HCl(aq) + Na2CO3(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
v)
Acids react with a metal hydrogencarbonate to form
salt, carbon dioxide and water.
HCl(aq) + NaHCO3(aq) → NaCl(aq) + CO2(g) + H2O(l)
16
vi)
Acids react with a metal sulfite to form salt, sulfur
dioxide and water
2HCl(aq) + Na2SO3(aq) → 2NaCl(aq) + SO2(g) + H2O(l)

Uses of acids:
۞
Hydrochloric acid is used in
۞
۞
i)
Leather processing
ii)
Cleaning metals
Sulfuric acid is used in
i)
Making detergents
ii)
Car batteries
iii)
Fertilisers
iv)
Making paint and pigments
v)
Pickling (surface cleaning) of metals
vi)
Making natural and manmade fibre.
vii)
Making chemicals such as sulfates plastics etc.
Ethanoic acid is used in
i)
Preserve food (as vinegar)
ii)
Adhesives such as glue.

Bases:
۞
A base is a substance which contains either oxide or
hydroxide ion. E.g. MgO, NaOH, CuO, KOH.

Alkalis:
۞
An alkali is a substance which produces hydroxide ions as only
negatively charged ions when dissolved in water.
E.g. NaOH, KOH, Ca(OH)2 .
17


Physical properties of alkalis:
i)
Alkalis turn damp red litmus paper blue.
ii)
Alkalis are bitter in taste.
iii)
Alkalis have a pH greater than 7.
iv)
Alkalis are corrosive.
Chemical properties of alkalis /bases:
i)
Alkalis react with acids to form salt and water.
HCl(aq) + NaOH(aq) → NaCl(aq) +
ii)
H2O(l)
Alkalis react with ammonium salt to form salt, ammonia
gas and water.
NH4Cl(aq) + NaOH(aq) → NaCl(aq) + NH3(g) + H2O(l)
iii)
A base reacts with an acid to form salt and water.
MgO(s) + H2SO4 (aq) → MgSO4 (aq)
iv)
+
H2O(l)
Alkalis react with some metal ions in the solution to
form a precipitate (ppt) of metal hydroxide.
2NaOH(aq) + FeSO4(aq) → Fe(OH)2(s) + Na2SO4(aq)
Green ppt
18
 Uses of alkalis and bases:
۞
۞
۞
۞

۞
۞
۞
Sodium hydroxide is used in
i)
Making soap and detergents
ii)
Industrial cleaning detergents
Magnesium hydroxide is used in
i)
Toothpaste to neutralize acid on teeth
ii)
Antacids to relieve indigestion
Calcium oxide is used in
i)
Neutralising acidic salt
ii)
Iron, concreate and cement
Ammonia solution is used in
i)
Fertilisers
ii)
Window cleaning solutions
pH: It is the measure of acidity or alkalinity of an aqueous solution.
pH range is 0 to 14.
pH scale:
Summary of pH scale:
pH < 7, the solution is acidic
pH = 7, the solution is neutral
pH > 7, the solution is alkaline
19
 Indicators:
۞ An indicator is a substance that changes colour with the change in pH
of the solution. E.g. Litmus, Methyl orange.
Sl.
Name of the indicator
No.
Colour in the
Colour in the
acidic medium
alkaline medium
01
Litmus
Red
Blue
02
Methyl orange
Red
Yellow
03
Phenolphthalein
Colourless
Pink
 Universal indicator:
pH
Colour
0-4
R
5
O
6
Y
7
G
8
B
9
I
10-14
V
04. WRITING FORMULAE:
 Valence or Valency:
۞
The valence or valency of an element is a measure of its combining
power with other atoms when it forms chemical compounds or
molecules.
The following rules apply to IONIC BONDING:
i)
Group 1 elements become +1.
E.g. Li+, Na+, K+.
ii)
Group 2 elements become +2.
E.g. Mg+2, Ca+2 (Write +2 or 2+).
iii)
Group 3 elements become +3.
E.g. Al+3.
20
iv)
Group 4 elements: You will not have to give those charges.
v)
Group 5 elements become -3:
E.g. N-3.
vi)
Group 6 elements become -2.
E.g. O-2, S-2.
vii)
Group 7 elements become -1.
E.g. F-, Cl-, Br-, I-.
viii)
Group 8/0 elements do not bond.
They are stable → Noble gases. (He,Ne, Ar).
ix)
Transition elements (between groups 2 and 3) have a charge
of +2, except silver (Ag+ ). Cu+2, Pb+2, Sn+2, Zn+2.
 The positive charges must equal all negative charges in an ionic
compound.

Radicals:
۞
An atom or a group of atoms which forms a part of an
inorganic compound is called a radical.
۞
Radicals with valency:
Name of the
ion/radical
Formula with
valency
Ammonium ion
NH4
Hydroxide ion
OH
Nitrate ion
NO3
Nitrite ion
NO2
Name of the
ion/radical
Formula with
valency
+
Sulfate ion
SO4
2-
-
Sulfite ion
SO3
-
Carbonate ion
CO3
-
Sulfide
S
2-
2-
2-
21
۞
Radicals with valency:
Name of the
ion/radical
Hydrogensulfite
ion
Hydrogensulfate
ion
Nitride ion
Name of the
ion/radical
Formula with
valency
-
Hydrogencarbonate
ion
HCO3
-
Phosphate ion
PO4
Hydrogenphophate
HPO4
Formula with
valency
HSO3
HSO4
N
3-
ion

-
3-
2-
Steps for writing and balancing the formula:
i)
Identify the cation (the portion with a positive charge).
ii)
Identify the anion (the portion with a negative charge).
iii)
Write the cation first, followed by the anion.
iv)
Adjust the subscripts of the cation and anion so the
net charge is 0.

The Crossover method:
۞
Cross the absolute value of the cation’s charge to the subscript
of the anion and cross the absolute value of the anion’s charge to
the subscript of the cation. e.g. Potassium chloride.
Correct formula is KCl.
22

Ions with different charges:
۞
Calcium chloride:
Ca2+ 2Cl-
•
Correct formula is CaCl2
Aluminium sulfate:
۞
۞
•
•
(Al3+)2
•
Correct formula is Al2(SO4)3
(SO42-)3
Can you try ?
01.
Sodium chloride
02.
Potassium nitrate
03.
Potassium hydroxide
04.
Lithium nitrite
05.
Sodium sulfate
06.
Sodium sulfite
07.
Calcium nitrate
08.
Magnesium sulfate
09.
Silver chloride
10.
Potassium carbonate
11.
Sodium hydrogencarbonate
12.
Silver carbonate
13.
Potassium phosphate
14.
Calcium hydrogensulfate
15.
Magnesium hydrogencarbonate
16.
Aluminium chloride
17.
Aluminium carbonate
18.
Aluminium sulfate
19.
Aluminium phosphate
20.
Sodium carbonate
21.
Sodium phosphate
22.
Sodium nitrate
23.
Sodium nitrite
24.
Sodium sulfite
25.
Ammonium chloride
26.
Ammonium nitrate
27.
Ammonium sulfate
23
28.
Ammonium phosphate
29.
Silver nitrate
30.
Silver chloride
31.
Silver bromide
32.
Silver iodide
33.
Potassium chloride
34.
Potassium bromide
35.
Potassium iodide
36.
Potassium hydrogensulfate
37.
Potassium sulfate
38.
Potassium hydrogencarbonate
39.
Potassium sulfite
40.
Calcium sulfate
42.
Iron (II) oxide
43.
Iron (III) oxide
44.
Iron (II) sulfate
45.
Iron (III) sulfate
46.
Iron (II) chloride
47.
Iron (III) chloride
48.
Iron (II) phosphate
49.
Iron (III) phosphate
50.
Copper (I) oxide
51.
Copper (II) oxide
52.
Copper (I) chloride
53.
Copper (II) chloride
54.
Copper (II) nitrate
55.
Copper (II) carbonate
56.
Copper (II) sulfate
57.
Copper (II) phosphate
58.
Sodium oxide
59.
Potassium oxide
60.
Magnesium oxide
61.
Calcium oxide
62.
Aluminium oxide
63.
Lithium oxide
64.
Magnesium nitrate
65.
Magnesium bromide
66.
Zinc chloride
67.
Zinc carbonate
68.
Zinc sulfate
69.
Zinc nitrate
70.
Zinc oxide
41. Calcium sulfite
24
05. IONIC EQUATIONS:

An ionic equation is a simplified chemical equation that shows the
reactions of such substances in water.
۞
An ionic equation shows the ions taking part in a reaction and the
products formed . It leaves out the spectator/common ions that do
not react.

Steps in writing an ionic equation:
i)
Write the balanced chemical equation of the reaction.
Include state symbols.
ii)
Identify ionic compounds that are soluble in water.
These compounds become ions in water. Rewrite the
equation in terms of ions.

iii)
Cancel out spectator/common ions.
iv)
Write the ionic equation.
Examples:
i)
Neutralisation reaction:
HCl(aq) + NaOH(aq) → NaCl(aq) +
H2O(l)
After ionization:
H+(aq) + Cl–(aq) + Na+(aq) + OH–(aq) →
Na+(aq) + Cl–(aq) + H2O(l)

Cancel out spectator ions.
The ionic equation is:
H+(aq) + OH–(aq)
→ H2O(l)
25
ii)
Metal reacts with acid:
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)
Zn(s) + 2H2+(aq) + SO42-(aq)

→
Zn2+(aq) + SO42-(aq) + H2(g)
The ionic equation is:
Zn(s) + 2H2+(aq) → Zn2+(aq) + H2(g)
iii)
Metal carbonate reacts with acid:
2HCl(aq) + Na2CO3(aq)
NaCl(aq) + CO2(g) + H2O(l)
→
2H2+(aq) + 2Cl-(aq) + 2Na+(aq) + CO32- (aq)
→
2Na+(aq) + 2Cl-(aq) + CO2(g) + H2O(l)

The ionic equation is:
2H2+(aq) + CO32- (aq)
iv)
→ CO2(g) + H2O(l)
Metal sulfite reacts with acid:
2HCl(aq) + Na2SO3(aq) →
NaCl(aq) + SO2(g) + H2O(l)
2H2+(aq) + 2Cl-(aq) + 2Na+(aq) + SO32- (aq)
→
2Na+(aq) + 2Cl-(aq) + SO2(g) + H2O(l)

Ionic equation is:
2H2+(aq) + SO32- (aq)
→
SO2(g) + H2O(l)
26
۞
Can you try ?
i)
CuO(s) + H2SO4 (aq) → CuSO4 (aq)
ii)
HCl(aq) + NaHCO3(aq) → NaCl(aq) + CO2(g) + H2O(l)
iii)
NH4Cl(aq) + NaOH(aq) → NaCl(aq) + NH3(g) + H2O(l)
iv)
2NaOH(aq) + FeSO4(aq) → Fe(OH)2(s) + Na2SO4(aq)
v)
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
vi)
AgNO3(aq) + NaBr(aq) → AgBr(s) + NaNO3(aq)
vii)
AgNO3(aq) + NaI(aq) → AgI(s) + NaNO3(aq)
viii)
Zn(s) + CuSO4 (aq) → ZnSO4 (aq) + Cu(s)
ix)
Ba(NO3)2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaNO3(aq)
x)
FeCl3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaCl(aq)
+
H2O(l)