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UNIT 1
SOME BASIC CONCEPTS OF CHEMISTRY
Science can be viewed as a continuing human effort to 
systematise knowledge for describing and understanding 
nature. You have learnt in your previous classes that we 
come across diverse substances present in nature and 
changes in them in daily life. Curd formation from milk, 
formation of vinegar from sugarcane juice on keeping 
for prolonged time and rusting of iron are some of the 
examples of changes which we come across many times. 
For the sake of convenience, science is sub-divided into 
various disciplines: chemistry, physics, biology, geology, 
etc. The branch of science that studies the preparation, 
properties, structure and reactions of material substances 
is called chemistry.
DEVELOPMENT OF CHEMISTRY
Chemistry, as we understand it today, is not a very old 
discipline. Chemistry was not studied for its own sake, rather 
it came up as a result of search for two interesting things:
 i. Philosopher’s stone (Paras) which would convert 
all baser metals e.g., iron and copper into gold.
 ii. ‘Elixir of life’ which would grant immortality.
People in ancient India, already had the knowledge of 
many scientific phenomenon much before the advent of 
modern science. They applied that knowledge in various 
walks of life. Chemistry developed mainly in the form 
of Alchemy and Iatrochemistry during 1300-1600 CE. 
Modern chemistry took shape in the 18
th
 century Europe, 
after a few centuries of alchemical traditions which were 
introduced in Europe by the Arabs. 
After studying this unit, you will be 
able to
• appreciate the contribution of India 
in the development of chemistry 
understand the role of chemistry 
in different spheres of life;
• explain the characteristics of three 
states of matter;
• classify different substances 
into elements, compounds and 
mixtures;
• use scientific notations and 
determine significant figures;
• differentiate between precision and 
accuracy;
• define SI base units and convert 
physical quantities from one 
system of units to another;
• explain various laws of chemical 
combination;
• appreciate significance of atomic 
mass, average atomic mass, 
molecular mass and formula mass;
• describe the terms – mole and 
molar mass;
• calculate the mass per cent of 
component elements constituting 
a compound;
• determine empirical formula and 
molecular formula for a compound 
from the given experimental data; 
and
• perform the stoichiometric 
calculations. 
Chemistry is the science of molecules and their 
transformations. It is the science not so much of the one 
hundred elements but of the infinite variety of molecules 
that may be built from them.
Roald Hoffmann
2024-25
Page 2


UNIT 1
SOME BASIC CONCEPTS OF CHEMISTRY
Science can be viewed as a continuing human effort to 
systematise knowledge for describing and understanding 
nature. You have learnt in your previous classes that we 
come across diverse substances present in nature and 
changes in them in daily life. Curd formation from milk, 
formation of vinegar from sugarcane juice on keeping 
for prolonged time and rusting of iron are some of the 
examples of changes which we come across many times. 
For the sake of convenience, science is sub-divided into 
various disciplines: chemistry, physics, biology, geology, 
etc. The branch of science that studies the preparation, 
properties, structure and reactions of material substances 
is called chemistry.
DEVELOPMENT OF CHEMISTRY
Chemistry, as we understand it today, is not a very old 
discipline. Chemistry was not studied for its own sake, rather 
it came up as a result of search for two interesting things:
 i. Philosopher’s stone (Paras) which would convert 
all baser metals e.g., iron and copper into gold.
 ii. ‘Elixir of life’ which would grant immortality.
People in ancient India, already had the knowledge of 
many scientific phenomenon much before the advent of 
modern science. They applied that knowledge in various 
walks of life. Chemistry developed mainly in the form 
of Alchemy and Iatrochemistry during 1300-1600 CE. 
Modern chemistry took shape in the 18
th
 century Europe, 
after a few centuries of alchemical traditions which were 
introduced in Europe by the Arabs. 
After studying this unit, you will be 
able to
• appreciate the contribution of India 
in the development of chemistry 
understand the role of chemistry 
in different spheres of life;
• explain the characteristics of three 
states of matter;
• classify different substances 
into elements, compounds and 
mixtures;
• use scientific notations and 
determine significant figures;
• differentiate between precision and 
accuracy;
• define SI base units and convert 
physical quantities from one 
system of units to another;
• explain various laws of chemical 
combination;
• appreciate significance of atomic 
mass, average atomic mass, 
molecular mass and formula mass;
• describe the terms – mole and 
molar mass;
• calculate the mass per cent of 
component elements constituting 
a compound;
• determine empirical formula and 
molecular formula for a compound 
from the given experimental data; 
and
• perform the stoichiometric 
calculations. 
Chemistry is the science of molecules and their 
transformations. It is the science not so much of the one 
hundred elements but of the infinite variety of molecules 
that may be built from them.
Roald Hoffmann
2024-25
2 chemistry Other cultures – especially the Chinese 
and the Indian – had their own alchemical 
traditions. These included much knowledge of 
chemical processes and techniques.
In ancient India, chemistry was called 
Rasayan Shastra, Rastantra, Ras Kriya or 
Rasvidya. It included metallurgy, medicine, 
manufacture of cosmetics, glass, dyes, etc. 
Systematic excavations at Mohenjodaro in 
Sindh and Harappa in Punjab prove that the 
story of development of chemistry in India 
is very old. Archaeological findings show 
that baked bricks were used in construction 
work. It shows the mass production of 
pottery, which can be regarded as the earliest 
chemical process, in which materials were 
mixed, moulded and subjected to heat by 
using fire to achieve desirable qualities. 
Remains of glazed pottery have been found in  
Mohenjodaro. Gypsum cement has been used 
in the construction work. It contains lime, 
sand and traces of CaCO
3
.
 
Harappans made 
faience, a sort of glass which was used in 
ornaments. They melted and forged a variety 
of objects from metals, such as lead, silver, 
gold and copper. They improved the hardness 
of copper for making artefacts by using tin 
and arsenic. A number of glass objects were 
found in Maski in South India (1000–900 
BCE), and  Hastinapur and Taxila in North 
India (1000–200 BCE). Glass and glazes were 
coloured by addition of colouring agents like 
metal oxides.
Copper metallurgy in India dates back to 
the beginning of chalcolithic cultures in the 
subcontinent. There are much archeological 
evidences to support the view that technologies 
for extraction of copper and iron were 
developed indigenously.
According to Rigveda, tanning of leather 
and dying of cotton were practised during 
1000–400 BCE. The golden gloss of the 
black polished ware of northen India could 
not  be replicated and is still a chemical 
mystery. These wares indicate the mastery 
with which kiln temperatures could be 
controlled. Kautilya’s Arthashastra describes 
the production of salt from sea.
A vast number of statements and material 
described in the ancient Vedic literature can 
be shown to agree with modern scientific 
findings. Copper utensils, iron, gold, silver 
ornaments and terracotta discs and painted 
grey pottery have been found in many 
archaeological sites in north India. Sushruta 
Samhita explains the importance of Alkalies. 
The Charaka Samhita mentions ancient 
indians who knew how to prepare sulphuric 
acid, nitric acid and oxides of copper, tin and 
zinc; the sulphates of copper, zinc and iron 
and the carbonates of lead and iron.
Rasopanishada describes the preparation 
of gunpowder mixture. Tamil texts also 
describe the preparation of fireworks using 
sulphur, charcoal, saltpetre (i.e., potassium 
nitrate), mercury, camphor, etc.
Nagarjuna was a great Indian scientist. He 
was a reputed chemist, an alchemist and a 
metallurgist. His work Rasratnakar deals with 
the formulation of mercury compounds. He 
has also discussed methods for the extraction 
of metals, like gold, silver, tin and copper. A 
book, Rsarnavam, appeared around 800 CE. 
It discusses the uses of various furnaces, 
ovens and crucibles for different purposes. It 
describes methods by which metals could be 
identified by flame colour. 
Chakrapani discovered mercury sulphide. 
The credit for inventing soap also goes to him. 
He used mustard oil and some alkalies as 
ingredients for making soap. Indians began 
making soaps in the 18
th
 century CE. Oil of 
Eranda and seeds of Mahua plant and calcium 
carbonate were used for making soap.
The paintings found on the walls of Ajanta 
and Ellora, which look fresh even after ages, 
testify to a high level of science achieved in 
ancient India. Varähmihir’s Brihat Samhita is 
a sort of encyclopaedia, which was composed 
in the sixth century CE. It informs about the 
preparation of glutinous material to be applied 
on walls and roofs of houses and temples. It 
was prepared entirely from extracts of various 
plants, fruits, seeds and barks, which were 
concentrated by boiling, and then, treated 
with various resins. It will be interesting to 
test such materials scientifically and assess 
them for use. 
Unit 1.indd   2 9/9/2022   4:27:29 PM
2024-25
Page 3


UNIT 1
SOME BASIC CONCEPTS OF CHEMISTRY
Science can be viewed as a continuing human effort to 
systematise knowledge for describing and understanding 
nature. You have learnt in your previous classes that we 
come across diverse substances present in nature and 
changes in them in daily life. Curd formation from milk, 
formation of vinegar from sugarcane juice on keeping 
for prolonged time and rusting of iron are some of the 
examples of changes which we come across many times. 
For the sake of convenience, science is sub-divided into 
various disciplines: chemistry, physics, biology, geology, 
etc. The branch of science that studies the preparation, 
properties, structure and reactions of material substances 
is called chemistry.
DEVELOPMENT OF CHEMISTRY
Chemistry, as we understand it today, is not a very old 
discipline. Chemistry was not studied for its own sake, rather 
it came up as a result of search for two interesting things:
 i. Philosopher’s stone (Paras) which would convert 
all baser metals e.g., iron and copper into gold.
 ii. ‘Elixir of life’ which would grant immortality.
People in ancient India, already had the knowledge of 
many scientific phenomenon much before the advent of 
modern science. They applied that knowledge in various 
walks of life. Chemistry developed mainly in the form 
of Alchemy and Iatrochemistry during 1300-1600 CE. 
Modern chemistry took shape in the 18
th
 century Europe, 
after a few centuries of alchemical traditions which were 
introduced in Europe by the Arabs. 
After studying this unit, you will be 
able to
• appreciate the contribution of India 
in the development of chemistry 
understand the role of chemistry 
in different spheres of life;
• explain the characteristics of three 
states of matter;
• classify different substances 
into elements, compounds and 
mixtures;
• use scientific notations and 
determine significant figures;
• differentiate between precision and 
accuracy;
• define SI base units and convert 
physical quantities from one 
system of units to another;
• explain various laws of chemical 
combination;
• appreciate significance of atomic 
mass, average atomic mass, 
molecular mass and formula mass;
• describe the terms – mole and 
molar mass;
• calculate the mass per cent of 
component elements constituting 
a compound;
• determine empirical formula and 
molecular formula for a compound 
from the given experimental data; 
and
• perform the stoichiometric 
calculations. 
Chemistry is the science of molecules and their 
transformations. It is the science not so much of the one 
hundred elements but of the infinite variety of molecules 
that may be built from them.
Roald Hoffmann
2024-25
2 chemistry Other cultures – especially the Chinese 
and the Indian – had their own alchemical 
traditions. These included much knowledge of 
chemical processes and techniques.
In ancient India, chemistry was called 
Rasayan Shastra, Rastantra, Ras Kriya or 
Rasvidya. It included metallurgy, medicine, 
manufacture of cosmetics, glass, dyes, etc. 
Systematic excavations at Mohenjodaro in 
Sindh and Harappa in Punjab prove that the 
story of development of chemistry in India 
is very old. Archaeological findings show 
that baked bricks were used in construction 
work. It shows the mass production of 
pottery, which can be regarded as the earliest 
chemical process, in which materials were 
mixed, moulded and subjected to heat by 
using fire to achieve desirable qualities. 
Remains of glazed pottery have been found in  
Mohenjodaro. Gypsum cement has been used 
in the construction work. It contains lime, 
sand and traces of CaCO
3
.
 
Harappans made 
faience, a sort of glass which was used in 
ornaments. They melted and forged a variety 
of objects from metals, such as lead, silver, 
gold and copper. They improved the hardness 
of copper for making artefacts by using tin 
and arsenic. A number of glass objects were 
found in Maski in South India (1000–900 
BCE), and  Hastinapur and Taxila in North 
India (1000–200 BCE). Glass and glazes were 
coloured by addition of colouring agents like 
metal oxides.
Copper metallurgy in India dates back to 
the beginning of chalcolithic cultures in the 
subcontinent. There are much archeological 
evidences to support the view that technologies 
for extraction of copper and iron were 
developed indigenously.
According to Rigveda, tanning of leather 
and dying of cotton were practised during 
1000–400 BCE. The golden gloss of the 
black polished ware of northen India could 
not  be replicated and is still a chemical 
mystery. These wares indicate the mastery 
with which kiln temperatures could be 
controlled. Kautilya’s Arthashastra describes 
the production of salt from sea.
A vast number of statements and material 
described in the ancient Vedic literature can 
be shown to agree with modern scientific 
findings. Copper utensils, iron, gold, silver 
ornaments and terracotta discs and painted 
grey pottery have been found in many 
archaeological sites in north India. Sushruta 
Samhita explains the importance of Alkalies. 
The Charaka Samhita mentions ancient 
indians who knew how to prepare sulphuric 
acid, nitric acid and oxides of copper, tin and 
zinc; the sulphates of copper, zinc and iron 
and the carbonates of lead and iron.
Rasopanishada describes the preparation 
of gunpowder mixture. Tamil texts also 
describe the preparation of fireworks using 
sulphur, charcoal, saltpetre (i.e., potassium 
nitrate), mercury, camphor, etc.
Nagarjuna was a great Indian scientist. He 
was a reputed chemist, an alchemist and a 
metallurgist. His work Rasratnakar deals with 
the formulation of mercury compounds. He 
has also discussed methods for the extraction 
of metals, like gold, silver, tin and copper. A 
book, Rsarnavam, appeared around 800 CE. 
It discusses the uses of various furnaces, 
ovens and crucibles for different purposes. It 
describes methods by which metals could be 
identified by flame colour. 
Chakrapani discovered mercury sulphide. 
The credit for inventing soap also goes to him. 
He used mustard oil and some alkalies as 
ingredients for making soap. Indians began 
making soaps in the 18
th
 century CE. Oil of 
Eranda and seeds of Mahua plant and calcium 
carbonate were used for making soap.
The paintings found on the walls of Ajanta 
and Ellora, which look fresh even after ages, 
testify to a high level of science achieved in 
ancient India. Varähmihir’s Brihat Samhita is 
a sort of encyclopaedia, which was composed 
in the sixth century CE. It informs about the 
preparation of glutinous material to be applied 
on walls and roofs of houses and temples. It 
was prepared entirely from extracts of various 
plants, fruits, seeds and barks, which were 
concentrated by boiling, and then, treated 
with various resins. It will be interesting to 
test such materials scientifically and assess 
them for use. 
Unit 1.indd   2 9/9/2022   4:27:29 PM
2024-25
3 Some Ba Sic c oncept S of c hemi Stry A number of classical texts, like 
Atharvaveda (1000 BCE) mention some 
dye stuff, the material used were turmeric, 
madder, sunflower, orpiment, cochineal and 
lac. Some other substances having tinting 
property were kamplcica, pattanga and jatuka. 
Varähmihir’s Brihat Samhita gives 
references to perfumes and cosmetics. 
Recipes for hair dying were made from plants, 
like indigo and minerals like iron power, 
black iron or steel and acidic extracts of sour 
rice gruel. Gandhayukli describes recipes 
for making scents, mouth perfumes, bath 
powders, incense and talcum power.
Paper was known to India in the 17
th
 
century as account of Chinese traveller I-tsing 
describes. Excavations at Taxila indicate that 
ink was used in India from the fourth century. 
Colours of ink were made from chalk, red lead 
and minimum.
It seems that the process of fermentation 
was well-known to Indians. Vedas and 
Kautilya’s Arthashastra mention about 
many types of liquors. Charaka Samhita also 
mentions ingredients, such as barks of plants, 
stem, flowers, leaves, woods, cereals, fruits 
and sugarcane for making Asavas.
The concept that matter is ultimately 
made of indivisible building blocks, appeared 
in  India a few centuries BCE as a part of 
philosophical speculations. Acharya Kanda, 
born in 600 BCE, originally known by the 
name Kashyap, was the first proponent 
of the ‘atomic theory’. He formulated the 
theory of very small indivisible particles, 
which he named ‘Paramãnu’ (comparable 
to atoms). He authored the text Vaiseshika 
Sutras. According to him, all substances are 
aggregated form of smaller units called atoms 
(Paramãnu), which are eternal, indestructible, 
spherical, suprasensible and in motion in 
the original state. He explained that this 
individual entity cannot be sensed through 
any human organ. Kanda added that there 
are varieties of atoms that are as different as 
the different classes of substances. He said 
these (Paramãnu) could form pairs or triplets, 
among other combinations and unseen 
forces cause interaction between them. He 
conceptualised this theory around 2500 years 
before John Dalton (1766-1844). 
Charaka Samhita is the oldest Ayurvedic 
epic of India. It describes the treatment of 
diseases. The concept of reduction of particle 
size of metals is clearly discussed in Charaka 
Samhita. Extreme reduction of particle size is 
termed as nanotechnology. Charaka Samhita 
describes the use of bhasma of metals in the 
treatment of ailments. Now-a-days, it has 
been proved that bhasmas have nanoparticles 
of metals. 
After the decline of alchemy, Iatrochemistry 
reached a steady state, but it too declined due 
to the introduction and practise of western 
medicinal system in the 20
th
 century. During 
this period of stagnation, pharmaceutical 
industry based on Ayurveda continued to 
exist, but it too declined gradually. It took 
about 100-150 years for Indians to learn 
and adopt new techniques. During this time, 
foreign products poured in. As a result, 
indigenous traditional techniques gradually 
declined. Modern science appeared in Indian 
scene in the later part of the nineteenth 
century. By the mid-nineteenth century, 
European scientists started coming to India 
and modern chemistry started growing.
From the above discussion, you have learnt 
that chemistry deals with the composition, 
structure, properties and interection of matter 
and is of much use to human beings in daily 
life. These aspects can be best described and 
understood in terms of basic constituents of 
matter that are atoms and molecules. That 
is why, chemistry is also called the science of 
atoms and molecules. Can we see, weigh and 
perceive these entities (atoms and molecules)? 
Is it possible to count the number of atoms 
and molecules in a given mass of matter and 
have a quantitative relationship between the 
mass and the number of these particles? 
We will get the answer of some of these 
questions in this Unit. We will further describe 
how physical properties of matter can be 
quantitatively described using numerical 
values with suitable units. 
Unit 1.indd   3 9/9/2022   4:27:29 PM
2024-25
Page 4


UNIT 1
SOME BASIC CONCEPTS OF CHEMISTRY
Science can be viewed as a continuing human effort to 
systematise knowledge for describing and understanding 
nature. You have learnt in your previous classes that we 
come across diverse substances present in nature and 
changes in them in daily life. Curd formation from milk, 
formation of vinegar from sugarcane juice on keeping 
for prolonged time and rusting of iron are some of the 
examples of changes which we come across many times. 
For the sake of convenience, science is sub-divided into 
various disciplines: chemistry, physics, biology, geology, 
etc. The branch of science that studies the preparation, 
properties, structure and reactions of material substances 
is called chemistry.
DEVELOPMENT OF CHEMISTRY
Chemistry, as we understand it today, is not a very old 
discipline. Chemistry was not studied for its own sake, rather 
it came up as a result of search for two interesting things:
 i. Philosopher’s stone (Paras) which would convert 
all baser metals e.g., iron and copper into gold.
 ii. ‘Elixir of life’ which would grant immortality.
People in ancient India, already had the knowledge of 
many scientific phenomenon much before the advent of 
modern science. They applied that knowledge in various 
walks of life. Chemistry developed mainly in the form 
of Alchemy and Iatrochemistry during 1300-1600 CE. 
Modern chemistry took shape in the 18
th
 century Europe, 
after a few centuries of alchemical traditions which were 
introduced in Europe by the Arabs. 
After studying this unit, you will be 
able to
• appreciate the contribution of India 
in the development of chemistry 
understand the role of chemistry 
in different spheres of life;
• explain the characteristics of three 
states of matter;
• classify different substances 
into elements, compounds and 
mixtures;
• use scientific notations and 
determine significant figures;
• differentiate between precision and 
accuracy;
• define SI base units and convert 
physical quantities from one 
system of units to another;
• explain various laws of chemical 
combination;
• appreciate significance of atomic 
mass, average atomic mass, 
molecular mass and formula mass;
• describe the terms – mole and 
molar mass;
• calculate the mass per cent of 
component elements constituting 
a compound;
• determine empirical formula and 
molecular formula for a compound 
from the given experimental data; 
and
• perform the stoichiometric 
calculations. 
Chemistry is the science of molecules and their 
transformations. It is the science not so much of the one 
hundred elements but of the infinite variety of molecules 
that may be built from them.
Roald Hoffmann
2024-25
2 chemistry Other cultures – especially the Chinese 
and the Indian – had their own alchemical 
traditions. These included much knowledge of 
chemical processes and techniques.
In ancient India, chemistry was called 
Rasayan Shastra, Rastantra, Ras Kriya or 
Rasvidya. It included metallurgy, medicine, 
manufacture of cosmetics, glass, dyes, etc. 
Systematic excavations at Mohenjodaro in 
Sindh and Harappa in Punjab prove that the 
story of development of chemistry in India 
is very old. Archaeological findings show 
that baked bricks were used in construction 
work. It shows the mass production of 
pottery, which can be regarded as the earliest 
chemical process, in which materials were 
mixed, moulded and subjected to heat by 
using fire to achieve desirable qualities. 
Remains of glazed pottery have been found in  
Mohenjodaro. Gypsum cement has been used 
in the construction work. It contains lime, 
sand and traces of CaCO
3
.
 
Harappans made 
faience, a sort of glass which was used in 
ornaments. They melted and forged a variety 
of objects from metals, such as lead, silver, 
gold and copper. They improved the hardness 
of copper for making artefacts by using tin 
and arsenic. A number of glass objects were 
found in Maski in South India (1000–900 
BCE), and  Hastinapur and Taxila in North 
India (1000–200 BCE). Glass and glazes were 
coloured by addition of colouring agents like 
metal oxides.
Copper metallurgy in India dates back to 
the beginning of chalcolithic cultures in the 
subcontinent. There are much archeological 
evidences to support the view that technologies 
for extraction of copper and iron were 
developed indigenously.
According to Rigveda, tanning of leather 
and dying of cotton were practised during 
1000–400 BCE. The golden gloss of the 
black polished ware of northen India could 
not  be replicated and is still a chemical 
mystery. These wares indicate the mastery 
with which kiln temperatures could be 
controlled. Kautilya’s Arthashastra describes 
the production of salt from sea.
A vast number of statements and material 
described in the ancient Vedic literature can 
be shown to agree with modern scientific 
findings. Copper utensils, iron, gold, silver 
ornaments and terracotta discs and painted 
grey pottery have been found in many 
archaeological sites in north India. Sushruta 
Samhita explains the importance of Alkalies. 
The Charaka Samhita mentions ancient 
indians who knew how to prepare sulphuric 
acid, nitric acid and oxides of copper, tin and 
zinc; the sulphates of copper, zinc and iron 
and the carbonates of lead and iron.
Rasopanishada describes the preparation 
of gunpowder mixture. Tamil texts also 
describe the preparation of fireworks using 
sulphur, charcoal, saltpetre (i.e., potassium 
nitrate), mercury, camphor, etc.
Nagarjuna was a great Indian scientist. He 
was a reputed chemist, an alchemist and a 
metallurgist. His work Rasratnakar deals with 
the formulation of mercury compounds. He 
has also discussed methods for the extraction 
of metals, like gold, silver, tin and copper. A 
book, Rsarnavam, appeared around 800 CE. 
It discusses the uses of various furnaces, 
ovens and crucibles for different purposes. It 
describes methods by which metals could be 
identified by flame colour. 
Chakrapani discovered mercury sulphide. 
The credit for inventing soap also goes to him. 
He used mustard oil and some alkalies as 
ingredients for making soap. Indians began 
making soaps in the 18
th
 century CE. Oil of 
Eranda and seeds of Mahua plant and calcium 
carbonate were used for making soap.
The paintings found on the walls of Ajanta 
and Ellora, which look fresh even after ages, 
testify to a high level of science achieved in 
ancient India. Varähmihir’s Brihat Samhita is 
a sort of encyclopaedia, which was composed 
in the sixth century CE. It informs about the 
preparation of glutinous material to be applied 
on walls and roofs of houses and temples. It 
was prepared entirely from extracts of various 
plants, fruits, seeds and barks, which were 
concentrated by boiling, and then, treated 
with various resins. It will be interesting to 
test such materials scientifically and assess 
them for use. 
Unit 1.indd   2 9/9/2022   4:27:29 PM
2024-25
3 Some Ba Sic c oncept S of c hemi Stry A number of classical texts, like 
Atharvaveda (1000 BCE) mention some 
dye stuff, the material used were turmeric, 
madder, sunflower, orpiment, cochineal and 
lac. Some other substances having tinting 
property were kamplcica, pattanga and jatuka. 
Varähmihir’s Brihat Samhita gives 
references to perfumes and cosmetics. 
Recipes for hair dying were made from plants, 
like indigo and minerals like iron power, 
black iron or steel and acidic extracts of sour 
rice gruel. Gandhayukli describes recipes 
for making scents, mouth perfumes, bath 
powders, incense and talcum power.
Paper was known to India in the 17
th
 
century as account of Chinese traveller I-tsing 
describes. Excavations at Taxila indicate that 
ink was used in India from the fourth century. 
Colours of ink were made from chalk, red lead 
and minimum.
It seems that the process of fermentation 
was well-known to Indians. Vedas and 
Kautilya’s Arthashastra mention about 
many types of liquors. Charaka Samhita also 
mentions ingredients, such as barks of plants, 
stem, flowers, leaves, woods, cereals, fruits 
and sugarcane for making Asavas.
The concept that matter is ultimately 
made of indivisible building blocks, appeared 
in  India a few centuries BCE as a part of 
philosophical speculations. Acharya Kanda, 
born in 600 BCE, originally known by the 
name Kashyap, was the first proponent 
of the ‘atomic theory’. He formulated the 
theory of very small indivisible particles, 
which he named ‘Paramãnu’ (comparable 
to atoms). He authored the text Vaiseshika 
Sutras. According to him, all substances are 
aggregated form of smaller units called atoms 
(Paramãnu), which are eternal, indestructible, 
spherical, suprasensible and in motion in 
the original state. He explained that this 
individual entity cannot be sensed through 
any human organ. Kanda added that there 
are varieties of atoms that are as different as 
the different classes of substances. He said 
these (Paramãnu) could form pairs or triplets, 
among other combinations and unseen 
forces cause interaction between them. He 
conceptualised this theory around 2500 years 
before John Dalton (1766-1844). 
Charaka Samhita is the oldest Ayurvedic 
epic of India. It describes the treatment of 
diseases. The concept of reduction of particle 
size of metals is clearly discussed in Charaka 
Samhita. Extreme reduction of particle size is 
termed as nanotechnology. Charaka Samhita 
describes the use of bhasma of metals in the 
treatment of ailments. Now-a-days, it has 
been proved that bhasmas have nanoparticles 
of metals. 
After the decline of alchemy, Iatrochemistry 
reached a steady state, but it too declined due 
to the introduction and practise of western 
medicinal system in the 20
th
 century. During 
this period of stagnation, pharmaceutical 
industry based on Ayurveda continued to 
exist, but it too declined gradually. It took 
about 100-150 years for Indians to learn 
and adopt new techniques. During this time, 
foreign products poured in. As a result, 
indigenous traditional techniques gradually 
declined. Modern science appeared in Indian 
scene in the later part of the nineteenth 
century. By the mid-nineteenth century, 
European scientists started coming to India 
and modern chemistry started growing.
From the above discussion, you have learnt 
that chemistry deals with the composition, 
structure, properties and interection of matter 
and is of much use to human beings in daily 
life. These aspects can be best described and 
understood in terms of basic constituents of 
matter that are atoms and molecules. That 
is why, chemistry is also called the science of 
atoms and molecules. Can we see, weigh and 
perceive these entities (atoms and molecules)? 
Is it possible to count the number of atoms 
and molecules in a given mass of matter and 
have a quantitative relationship between the 
mass and the number of these particles? 
We will get the answer of some of these 
questions in this Unit. We will further describe 
how physical properties of matter can be 
quantitatively described using numerical 
values with suitable units. 
Unit 1.indd   3 9/9/2022   4:27:29 PM
2024-25
4 chemistry 1.1 importance of chemi Stry
Chemistry plays a central role in science and 
is often intertwined with other branches of 
science.
Principles of chemistry are applicable 
in diverse areas, such as weather patterns, 
functioning of brain and operation of a 
computer, production in chemical industries, 
manufacturing fertilisers, alkalis, acids, salts, 
dyes, polymers, drugs, soaps, detergents, 
metals, alloys, etc., including new material.
Chemistry contributes in a big way to the 
national economy. It also plays an important 
role in meeting human needs for food, 
healthcare products and other material 
aimed at improving the quality of life.  This 
is exemplified by the large-scale production 
of a variety of fertilisers, improved variety 
of pesticides and insecticides. Chemistry 
provides methods for the isolation of life-
saving drugs from natural sources and 
makes possible synthesis of such drugs. 
Some of these drugs are cisplatin and 
taxol, which are effective in cancer therapy. 
The drug AZT (Azidothymidine) is used for 
helping AIDS patients. 
Chemistry contributes to a large extent in 
the development and growth of a nation. With 
a better understanding of chemical principles 
it has now become possible to design and 
synthesise new material having specific 
magnetic, electric and optical properties.  This 
has lead to the production of superconducting 
ceramics, conducting polymers, optical fibres, 
etc. Chemistry has helped in establishing 
industries which manufacture utility goods, 
like acids, alkalies, dyes, polymesr metals, 
etc. These industries contribute in a big way 
to the economy of a nation and generate 
employment. 
In recent years, chemistry has helped in 
dealing with some of the pressing aspects 
of environmental degradation with a fair 
degree of success. Safer alternatives to 
environmentally hazardous refrigerants, 
like CFCs (chlorofluorocarbons), responsible 
for ozone depletion in the stratosphere, have 
been successfully synthesised. However, 
many big environmental problems continue to 
be matters of grave concern to the chemists. 
One such problem is the management of the 
Green House gases, like methane, carbon 
dioxide, etc. Understanding of biochemical 
processes, use of enzymes for large-scale 
production of chemicals and synthesis of new 
exotic material are some of the intellectual 
challenges for the future generation of 
chemists. A developing country, like India, 
needs talented and creative chemists for 
accepting such challenges. To be a good 
chemist and to accept such challanges, one 
needs to understand the basic concepts of 
chemistry, which begin with the concept of 
matter. Let us start with the nature of matter.
1.2 nat Ure of matter
You are already familiar with the term matter 
from your earlier classes. Anything which has 
mass and occupies space is called matter. 
Everything around us, for example, book, pen, 
pencil, water, air, all living beings, etc., are 
composed of matter. You know that they have 
mass and they occupy space. Let us recall the 
characteristics of the states of matter, which 
you learnt in your previous classes.
1.2.1 States of matter
You are aware that matter can exist in three 
physical states viz. solid, liquid and gas. 
The constituent particles of matter in these 
three states can be represented as shown in 
Fig. 1.1.
Particles are held very close to each other 
in solids in an orderly fashion and there is not 
much freedom of movement. In liquids, the 
particles are close to each other but they can 
move around. However, in gases, the particles 
are far apart as compared to those present in 
solid or liquid states and their movement is 
easy and fast. Because of such arrangement 
of particles, different states of matter exhibit 
the following characteristics:
(i) Solids have definite volume and definite 
shape.
(ii) Liquids have definite volume but do 
not have definite shape . They take the 
shape of the container in which they are 
placed.
Unit 1.indd   4 9/9/2022   4:27:29 PM
2024-25
Page 5


UNIT 1
SOME BASIC CONCEPTS OF CHEMISTRY
Science can be viewed as a continuing human effort to 
systematise knowledge for describing and understanding 
nature. You have learnt in your previous classes that we 
come across diverse substances present in nature and 
changes in them in daily life. Curd formation from milk, 
formation of vinegar from sugarcane juice on keeping 
for prolonged time and rusting of iron are some of the 
examples of changes which we come across many times. 
For the sake of convenience, science is sub-divided into 
various disciplines: chemistry, physics, biology, geology, 
etc. The branch of science that studies the preparation, 
properties, structure and reactions of material substances 
is called chemistry.
DEVELOPMENT OF CHEMISTRY
Chemistry, as we understand it today, is not a very old 
discipline. Chemistry was not studied for its own sake, rather 
it came up as a result of search for two interesting things:
 i. Philosopher’s stone (Paras) which would convert 
all baser metals e.g., iron and copper into gold.
 ii. ‘Elixir of life’ which would grant immortality.
People in ancient India, already had the knowledge of 
many scientific phenomenon much before the advent of 
modern science. They applied that knowledge in various 
walks of life. Chemistry developed mainly in the form 
of Alchemy and Iatrochemistry during 1300-1600 CE. 
Modern chemistry took shape in the 18
th
 century Europe, 
after a few centuries of alchemical traditions which were 
introduced in Europe by the Arabs. 
After studying this unit, you will be 
able to
• appreciate the contribution of India 
in the development of chemistry 
understand the role of chemistry 
in different spheres of life;
• explain the characteristics of three 
states of matter;
• classify different substances 
into elements, compounds and 
mixtures;
• use scientific notations and 
determine significant figures;
• differentiate between precision and 
accuracy;
• define SI base units and convert 
physical quantities from one 
system of units to another;
• explain various laws of chemical 
combination;
• appreciate significance of atomic 
mass, average atomic mass, 
molecular mass and formula mass;
• describe the terms – mole and 
molar mass;
• calculate the mass per cent of 
component elements constituting 
a compound;
• determine empirical formula and 
molecular formula for a compound 
from the given experimental data; 
and
• perform the stoichiometric 
calculations. 
Chemistry is the science of molecules and their 
transformations. It is the science not so much of the one 
hundred elements but of the infinite variety of molecules 
that may be built from them.
Roald Hoffmann
2024-25
2 chemistry Other cultures – especially the Chinese 
and the Indian – had their own alchemical 
traditions. These included much knowledge of 
chemical processes and techniques.
In ancient India, chemistry was called 
Rasayan Shastra, Rastantra, Ras Kriya or 
Rasvidya. It included metallurgy, medicine, 
manufacture of cosmetics, glass, dyes, etc. 
Systematic excavations at Mohenjodaro in 
Sindh and Harappa in Punjab prove that the 
story of development of chemistry in India 
is very old. Archaeological findings show 
that baked bricks were used in construction 
work. It shows the mass production of 
pottery, which can be regarded as the earliest 
chemical process, in which materials were 
mixed, moulded and subjected to heat by 
using fire to achieve desirable qualities. 
Remains of glazed pottery have been found in  
Mohenjodaro. Gypsum cement has been used 
in the construction work. It contains lime, 
sand and traces of CaCO
3
.
 
Harappans made 
faience, a sort of glass which was used in 
ornaments. They melted and forged a variety 
of objects from metals, such as lead, silver, 
gold and copper. They improved the hardness 
of copper for making artefacts by using tin 
and arsenic. A number of glass objects were 
found in Maski in South India (1000–900 
BCE), and  Hastinapur and Taxila in North 
India (1000–200 BCE). Glass and glazes were 
coloured by addition of colouring agents like 
metal oxides.
Copper metallurgy in India dates back to 
the beginning of chalcolithic cultures in the 
subcontinent. There are much archeological 
evidences to support the view that technologies 
for extraction of copper and iron were 
developed indigenously.
According to Rigveda, tanning of leather 
and dying of cotton were practised during 
1000–400 BCE. The golden gloss of the 
black polished ware of northen India could 
not  be replicated and is still a chemical 
mystery. These wares indicate the mastery 
with which kiln temperatures could be 
controlled. Kautilya’s Arthashastra describes 
the production of salt from sea.
A vast number of statements and material 
described in the ancient Vedic literature can 
be shown to agree with modern scientific 
findings. Copper utensils, iron, gold, silver 
ornaments and terracotta discs and painted 
grey pottery have been found in many 
archaeological sites in north India. Sushruta 
Samhita explains the importance of Alkalies. 
The Charaka Samhita mentions ancient 
indians who knew how to prepare sulphuric 
acid, nitric acid and oxides of copper, tin and 
zinc; the sulphates of copper, zinc and iron 
and the carbonates of lead and iron.
Rasopanishada describes the preparation 
of gunpowder mixture. Tamil texts also 
describe the preparation of fireworks using 
sulphur, charcoal, saltpetre (i.e., potassium 
nitrate), mercury, camphor, etc.
Nagarjuna was a great Indian scientist. He 
was a reputed chemist, an alchemist and a 
metallurgist. His work Rasratnakar deals with 
the formulation of mercury compounds. He 
has also discussed methods for the extraction 
of metals, like gold, silver, tin and copper. A 
book, Rsarnavam, appeared around 800 CE. 
It discusses the uses of various furnaces, 
ovens and crucibles for different purposes. It 
describes methods by which metals could be 
identified by flame colour. 
Chakrapani discovered mercury sulphide. 
The credit for inventing soap also goes to him. 
He used mustard oil and some alkalies as 
ingredients for making soap. Indians began 
making soaps in the 18
th
 century CE. Oil of 
Eranda and seeds of Mahua plant and calcium 
carbonate were used for making soap.
The paintings found on the walls of Ajanta 
and Ellora, which look fresh even after ages, 
testify to a high level of science achieved in 
ancient India. Varähmihir’s Brihat Samhita is 
a sort of encyclopaedia, which was composed 
in the sixth century CE. It informs about the 
preparation of glutinous material to be applied 
on walls and roofs of houses and temples. It 
was prepared entirely from extracts of various 
plants, fruits, seeds and barks, which were 
concentrated by boiling, and then, treated 
with various resins. It will be interesting to 
test such materials scientifically and assess 
them for use. 
Unit 1.indd   2 9/9/2022   4:27:29 PM
2024-25
3 Some Ba Sic c oncept S of c hemi Stry A number of classical texts, like 
Atharvaveda (1000 BCE) mention some 
dye stuff, the material used were turmeric, 
madder, sunflower, orpiment, cochineal and 
lac. Some other substances having tinting 
property were kamplcica, pattanga and jatuka. 
Varähmihir’s Brihat Samhita gives 
references to perfumes and cosmetics. 
Recipes for hair dying were made from plants, 
like indigo and minerals like iron power, 
black iron or steel and acidic extracts of sour 
rice gruel. Gandhayukli describes recipes 
for making scents, mouth perfumes, bath 
powders, incense and talcum power.
Paper was known to India in the 17
th
 
century as account of Chinese traveller I-tsing 
describes. Excavations at Taxila indicate that 
ink was used in India from the fourth century. 
Colours of ink were made from chalk, red lead 
and minimum.
It seems that the process of fermentation 
was well-known to Indians. Vedas and 
Kautilya’s Arthashastra mention about 
many types of liquors. Charaka Samhita also 
mentions ingredients, such as barks of plants, 
stem, flowers, leaves, woods, cereals, fruits 
and sugarcane for making Asavas.
The concept that matter is ultimately 
made of indivisible building blocks, appeared 
in  India a few centuries BCE as a part of 
philosophical speculations. Acharya Kanda, 
born in 600 BCE, originally known by the 
name Kashyap, was the first proponent 
of the ‘atomic theory’. He formulated the 
theory of very small indivisible particles, 
which he named ‘Paramãnu’ (comparable 
to atoms). He authored the text Vaiseshika 
Sutras. According to him, all substances are 
aggregated form of smaller units called atoms 
(Paramãnu), which are eternal, indestructible, 
spherical, suprasensible and in motion in 
the original state. He explained that this 
individual entity cannot be sensed through 
any human organ. Kanda added that there 
are varieties of atoms that are as different as 
the different classes of substances. He said 
these (Paramãnu) could form pairs or triplets, 
among other combinations and unseen 
forces cause interaction between them. He 
conceptualised this theory around 2500 years 
before John Dalton (1766-1844). 
Charaka Samhita is the oldest Ayurvedic 
epic of India. It describes the treatment of 
diseases. The concept of reduction of particle 
size of metals is clearly discussed in Charaka 
Samhita. Extreme reduction of particle size is 
termed as nanotechnology. Charaka Samhita 
describes the use of bhasma of metals in the 
treatment of ailments. Now-a-days, it has 
been proved that bhasmas have nanoparticles 
of metals. 
After the decline of alchemy, Iatrochemistry 
reached a steady state, but it too declined due 
to the introduction and practise of western 
medicinal system in the 20
th
 century. During 
this period of stagnation, pharmaceutical 
industry based on Ayurveda continued to 
exist, but it too declined gradually. It took 
about 100-150 years for Indians to learn 
and adopt new techniques. During this time, 
foreign products poured in. As a result, 
indigenous traditional techniques gradually 
declined. Modern science appeared in Indian 
scene in the later part of the nineteenth 
century. By the mid-nineteenth century, 
European scientists started coming to India 
and modern chemistry started growing.
From the above discussion, you have learnt 
that chemistry deals with the composition, 
structure, properties and interection of matter 
and is of much use to human beings in daily 
life. These aspects can be best described and 
understood in terms of basic constituents of 
matter that are atoms and molecules. That 
is why, chemistry is also called the science of 
atoms and molecules. Can we see, weigh and 
perceive these entities (atoms and molecules)? 
Is it possible to count the number of atoms 
and molecules in a given mass of matter and 
have a quantitative relationship between the 
mass and the number of these particles? 
We will get the answer of some of these 
questions in this Unit. We will further describe 
how physical properties of matter can be 
quantitatively described using numerical 
values with suitable units. 
Unit 1.indd   3 9/9/2022   4:27:29 PM
2024-25
4 chemistry 1.1 importance of chemi Stry
Chemistry plays a central role in science and 
is often intertwined with other branches of 
science.
Principles of chemistry are applicable 
in diverse areas, such as weather patterns, 
functioning of brain and operation of a 
computer, production in chemical industries, 
manufacturing fertilisers, alkalis, acids, salts, 
dyes, polymers, drugs, soaps, detergents, 
metals, alloys, etc., including new material.
Chemistry contributes in a big way to the 
national economy. It also plays an important 
role in meeting human needs for food, 
healthcare products and other material 
aimed at improving the quality of life.  This 
is exemplified by the large-scale production 
of a variety of fertilisers, improved variety 
of pesticides and insecticides. Chemistry 
provides methods for the isolation of life-
saving drugs from natural sources and 
makes possible synthesis of such drugs. 
Some of these drugs are cisplatin and 
taxol, which are effective in cancer therapy. 
The drug AZT (Azidothymidine) is used for 
helping AIDS patients. 
Chemistry contributes to a large extent in 
the development and growth of a nation. With 
a better understanding of chemical principles 
it has now become possible to design and 
synthesise new material having specific 
magnetic, electric and optical properties.  This 
has lead to the production of superconducting 
ceramics, conducting polymers, optical fibres, 
etc. Chemistry has helped in establishing 
industries which manufacture utility goods, 
like acids, alkalies, dyes, polymesr metals, 
etc. These industries contribute in a big way 
to the economy of a nation and generate 
employment. 
In recent years, chemistry has helped in 
dealing with some of the pressing aspects 
of environmental degradation with a fair 
degree of success. Safer alternatives to 
environmentally hazardous refrigerants, 
like CFCs (chlorofluorocarbons), responsible 
for ozone depletion in the stratosphere, have 
been successfully synthesised. However, 
many big environmental problems continue to 
be matters of grave concern to the chemists. 
One such problem is the management of the 
Green House gases, like methane, carbon 
dioxide, etc. Understanding of biochemical 
processes, use of enzymes for large-scale 
production of chemicals and synthesis of new 
exotic material are some of the intellectual 
challenges for the future generation of 
chemists. A developing country, like India, 
needs talented and creative chemists for 
accepting such challenges. To be a good 
chemist and to accept such challanges, one 
needs to understand the basic concepts of 
chemistry, which begin with the concept of 
matter. Let us start with the nature of matter.
1.2 nat Ure of matter
You are already familiar with the term matter 
from your earlier classes. Anything which has 
mass and occupies space is called matter. 
Everything around us, for example, book, pen, 
pencil, water, air, all living beings, etc., are 
composed of matter. You know that they have 
mass and they occupy space. Let us recall the 
characteristics of the states of matter, which 
you learnt in your previous classes.
1.2.1 States of matter
You are aware that matter can exist in three 
physical states viz. solid, liquid and gas. 
The constituent particles of matter in these 
three states can be represented as shown in 
Fig. 1.1.
Particles are held very close to each other 
in solids in an orderly fashion and there is not 
much freedom of movement. In liquids, the 
particles are close to each other but they can 
move around. However, in gases, the particles 
are far apart as compared to those present in 
solid or liquid states and their movement is 
easy and fast. Because of such arrangement 
of particles, different states of matter exhibit 
the following characteristics:
(i) Solids have definite volume and definite 
shape.
(ii) Liquids have definite volume but do 
not have definite shape . They take the 
shape of the container in which they are 
placed.
Unit 1.indd   4 9/9/2022   4:27:29 PM
2024-25
5 Some Ba Sic c oncept S of c hemi Stry (iii) Gases have neither definite volume nor 
definite shape . They completely occupy 
the space in the container in which they 
are placed.
These three states of matter are 
interconvertible by changing the conditions 
of temperature and pressure.
Solid  liquid  Gas
On heating, a solid usually changes to 
a liquid, and the liquid on further heating 
changes to gas (or vapour). In the reverse 
process, a gas on cooling liquifies to the liquid 
and the liquid on further cooling freezes to 
the solid.
1.2.2.	 Classification 	 of	 Matter
In Class IX (Chapter 2), you have learnt that 
at the macroscopic or bulk level, matter can 
be classified as mixture or pure substance. 
These can be further sub-divided as shown 
in Fig. 1.2.
When all constituent particles of a 
substance are same in chemical nature, it 
is said to be a pure substance. A mixture 
contains many types of particles.
a mixture contains particles of two or 
more pure substances which may be present 
in it in any ratio. Hence, their composition is 
variable. Pure substances forming mixture 
are called its components. Many of the 
substances present around you are mixtures. 
For example, sugar solution in water, air, 
tea, etc., are all mixtures. A mixture may 
be homogeneous or heterogeneous. In a 
homogeneous mixture, the components 
Fig. 1.2  Classification of matter
Fig. 1.1 Arrangement of particles in solid, liquid 
and gaseous state
completely mix with each other. This means 
particles of components of the mixture are 
uniformly distributed throughout the bulk of 
the mixture and its composition is uniform 
throughout. Sugar solution and air are the 
examples of homogeneous mixtures. In 
contrast to this, in a heterogeneous mixture, 
the composition is not uniform throughout 
and sometimes different components are 
visible. For example, mixtures of salt and 
sugar, grains and pulses along with some 
dirt (often stone pieces), are heterogeneous 
mixtures. You can think of many more 
examples of mixtures which you come across 
in the daily life. It is worthwhile to mention 
here that the components of a mixture can 
be separated by using physical methods, 
such as simple hand-picking, filtration, 
crystallisation, distillation, etc. 
pure substances have characteristics 
different from mixtures. Constituent particles 
of pure substances have fixed composition. 
Copper, silver, gold, water and glucose are 
some examples of pure substances. Glucose 
contains carbon, hydrogen and oxygen in 
a fixed ratio and its particles are of same 
composition. Hence, like all other pure 
substances, glucose has a fixed composition. 
Also, its constituents—carbon, hydrogen 
and oxygen—cannot be separated by simple 
physical methods.
Pure substances can further be classified 
into elements and compounds. Particles 
of an element consist of only one type of 
atoms. These particles may exist as atoms or 
molecules. You may be familiar with atoms 
Unit 1.indd   5 9/9/2022   4:27:30 PM
2024-25
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FAQs on NCERT Textbook: Some Basic Concepts Of Chemistry - Chemistry Class 11 - NEET

1. What are the basic concepts of chemistry?
Ans. The basic concepts of chemistry include elements, compounds, mixtures, chemical reactions, and atomic structure. These concepts form the foundation of understanding chemical reactions and their applications in various fields.
2. How are elements different from compounds?
Ans. Elements are pure substances that cannot be broken down into simpler substances by chemical means. They are made up of only one type of atom. On the other hand, compounds are substances composed of two or more elements that are chemically combined in fixed ratios. Compounds can be broken down into simpler substances through chemical reactions.
3. What are mixtures? Provide examples.
Ans. Mixtures are substances that are composed of two or more pure substances physically combined. The components of a mixture can be separated by physical means, such as filtration or evaporation. Examples of mixtures include air (a mixture of gases), saltwater (a mixture of salt and water), and trail mix (a mixture of different types of nuts and dried fruits).
4. How do chemical reactions occur?
Ans. Chemical reactions occur when there is a rearrangement of atoms in the reactant molecules to form new products. This rearrangement involves breaking and forming chemical bonds. Chemical reactions can be represented by balanced chemical equations, which show the reactants on the left side and the products on the right side of the equation.
5. What is atomic structure?
Ans. Atomic structure refers to the arrangement and organization of subatomic particles within an atom. Atoms are composed of a positively charged nucleus, which contains protons and neutrons, surrounded by negatively charged electrons in energy levels or shells. The atomic structure determines the chemical properties and behavior of elements.
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