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Carbon and
Its Compounds
Carbon, a non-metal with atomic number 6 and mass number 12, occurs in
free as well as in combined form
...
Its amount in
the earth’s crust and in the atmosphere is quite meagre
...
02% carbon which is present as minerals and in the atmosphere 0
...
Carbon thus forms a large
number of compounds with itself and with the atoms of other elements; some of
which are studied in this chapter
...
e
...

The octet can be completed by following two ways
4+
(i) It could lose 4 electrons and form C cation
...

4−
(ii) It could gain 4 electrons and can form C anion
...
e
...

In order to overcome this problem, carbon shares its valence electrons with its
other atoms or atoms of other elements
...
This type of bonding is called
covalent bonding
...











Compounds: The Covalent
Bond
Allotropes of Carbon
Versatile Nature of
Carbon
Organic Compounds
Hydrocarbons
Functional Groups
Nomenclature of Carbon
Compounds
Chemical Properties of
Carbon Compounds
Fuels and Flames
Some Important Carbon
Compounds
Soaps and Detergents

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Shared electrons

The number of electrons shared show the covalency of that
atom
...


O

Examples

O

O

(i) Formation of Hydrogen Molecule

H

Covalent bonding in O2 molecule

Here, a double bond between two oxygen atoms
forming an oxygen molecule represents the sharing of
4 electrons
...
Thus, 2 nitrogen atoms share 3 each of
their electrons, forming a triple bond of nitrogen
molecule
...

H

≡≡ O== O

O

Oxygen molecule

Oxygen atoms

Atomic number of H = 1
It has 1 electron in its K shell and needs 1 more electron
to fill the K shell completely
...
Valence electrons are depicted by using
dots or crosses
...

It shows carbon is tetravalent because it possesses four
valence electrons and hydrogen is monovalent because it
has only one valence electron
...
This is
achieved by sharing of 1 electron with another Cl atom,
forming a chlorine molecule (Cl 2 )
...


(vi) Formation of Ammonia and Water Molecule
Ammonia (NH3 )
H

K L

H

N

≡≡ N—H

Electronic configuration = 2 , 6

It requires 2 electrons to fulfill its octet and attain noble
gas configuration
...


H

H

H

Ammonia (NH3 ) molecule

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3

Carbon and Its Compounds

Water (H 2O)
H

H
q

≡≡ H—O—H or O

O

H

H

Water (H2O ) molecule

Allotropes of Carbon

(vii) Formation of Carbon Dioxide (CO2 )

Some chemical elements can exist in two or more
different forms, which differ in arrangement of atoms and in
number of atoms but are chemically same
...

For example, Carbon exists in several allotropic forms like
diamond, graphite, buckminster fullerene, coal, charcoal,
etc
...


Atomic number of C = 6
K L

Electronic configuration = 2 4
Atomic number of O = 8

K L

Electronic configuration = 2 6

Thus, they complete their octet as
••
•
•
•O •

× ×
×C ×

••
•
•
•O •

••

→

O

••

• ×
• ×

ו
ו

C

••

O

••

O == C == O

or

(viii) Formation of Sulphur Molecule (S8 )
Atomic number of sulphur = 16
K L M

Electronic configuration = 2 8 6
So, the valency of each S atom is 2
...
However, graphite is an
exception of it, which is a good conductor of electricity
...


Properties of Covalent Compounds
Covalently bonded molecules are called covalent
compounds
...

q
They have strong bonds within the molecule but
intermolecular forces are weak, which is responsible for
the low melting and boiling points of these compounds
(graphite and diamond are exceptions of this)
...

q
It is quite heavy
...

q
It does not conduct electricity (because of the absence of
free electrons)
...

q
It burns on strong heating to form carbon dioxide
...
Moreover, a
lot of energy is required to break the network of strong
covalent bonds in the diamond crystal, thus its melting
point is very high
...

q
It is used for the purpose of ornaments studded as precious
stones
...

q
Dies made from diamond are used for drawing wires from
the metals
...
These synthetic diamonds are
small but are otherwise indistinguishable from natural diamonds
...

q
It is lighter than diamond, feels soft and slippery to touch
...

q
It burns on strong heating to form carbon dioxide
...
Each carbon atom in a graphite layer is
joined to three other carbon atoms by strong covalent bonds to
form flat hexagonal rings
...
The various layers of carbon atoms in graphite are
held together by weak van der Waals’ forces so these can slide
over one another
...
Most commonly known fullerene contains 60 C
atoms (C 60 ) with smaller proportion of C 70 and traces of
compounds containing even upto 370 carbon atoms
...

Properties
Properties of fullerenes are
q
These are dark solids at room temperature
...

q
These are the purest allotrophic forms of carbon
because of the absence of free valencies or surface
bonds
...

Other properties of fullerene are still being
investigated
...
One C 60 molecule
contains 20 hexagons and 12 pentagons of carbon atoms
...

q
It is used for making electrodes of cells
...
It is therefore called black lead or plumbago
...


Buckminster fullerene (C60 ) Structure

Uses
Uses of fullerene are
q
In pure form, these behave as insulators
...

q C
O, a molecule formed when C 60 traps O atoms, is
60
used in cancer as well as AIDS therapy
...


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Check

5

Carbon and Its Compounds

oint

1

1
...
Name the two properties of carbon which makes it
different from other elements
...
Why are covalent compounds bad conductor of
electricity?
4
...
Explain why?
5
...
But now the question is, which
property or properties of carbon is/are responsible for the
formation of such a large number of carbon compounds
...

These properties are
(i) Catenation (ii) Tetravalency

(i) Catenation
Carbon atoms have a unique ability to form bonds
(single, double as well as triple) with other carbon atoms to
form large molecules
...

This property of self linking of carbons atom through
covalent bonds to form straight chains or cyclic rings of
carbon atoms is called catenation
...


(ii) Tetravalency
Due to the valency of four, carbon is capable of bonding
or pairing with four other carbon atoms or with the atoms of

some other monovalent elements
...
This gives rise to compounds with specific
properties which depend on the element other than carbon
present in the molecule
...
The main
reason for such strong bond formation is the small size of
carbon
...

®

The strength of bond decreases with increase in the size of
atoms
...
These compounds were initially extracted from
natural substances and was believed that some vital force was
necessary for the synthesis of these compounds (vital force
theory)
...

(NH 4 ) 2 SO 4
Ammonium sulphate

+

2KCNO

∆

→

Potassium cyanate

2NH 4 CNO + K 2 SO 4
Ammonium
cyanate

Potassium
sulphate

∆

NH 4 CNO → NH 2CONH 2
Ammonium
cyanate

(Rearrangement)

Urea

Synthesis of acetic acid from its elements by Kolbe in
1845 also disproved the vital force theory
...
g
...
)

Hydrocarbons
(compounds having
carbon and hydrogen only)

C

C

H

H

H, CH4 (methane)
H
H

Heterocyclic
(have atleast one atom
other than carbon as a
part of the ring)
...
g
...
g
...
g
...
g
...
g
...
Their main sources
are petroleum (or crude oil) and natural gas
...


Saturated Hydrocarbons
The hydrocarbons in which all the carbon atoms are
connected by only single bonds are called saturated
hydrocarbons or alkanes or paraffins
...

For example, if there is only one carbon atom then its
formula should be C 1H 2 × 1+ 2 = CH 4 (methane)
...
e
...

These compounds generally show substitution reaction
(which are discussed later in this chapter)
...

These compounds generally burn with sooty flame due
to their incomplete combustion
...

Unsaturated compounds further divided into following two
classes
(i) Alkanes or Oleffins
Those carbon compounds which have atleast one double
bond alongwith single bonds are called alkanes
...

General formula of these compounds is C n H 2n
...

(ii) Alkynes
Those unsaturated hydrocarbons which have one or
more triple bonds alongwith the single bonds are called
alkynes
...

General formula of these compounds is C n H 2n − 2
...
If there are 3 carbon
atoms in the alkyne then its formula must be
C 3 H 2×3 − 2 = C 3 H 4
...


How to Draw the Structure of Saturated
and Unsaturated Compounds?
Step 1
Step 2
Step 3

7

Carbon and Its Compounds

To draw the structure of carbon compound, first
connect all the carbon atoms by a single bond
...

If number of available H-atoms are less than that
required, satisfy the remaining valency by using
double or triple bond
...


Each of these unsatisfied valencies are satisfied by
hydrogen atoms
...

Electron dot structure of ethane (C 2H 6 )
H
C

C

H

H

H

H

H

(ii) Structure of Propane (C 3H8 )
Same rules are followed as in case of ethane
...

H H H
  
[II step]
H C  C  C H
  
H H H
Two C-atoms are bonded to 3 hydrogen atoms and one
carbon atom is bonded to 2 hydrogen atoms
...
To satisfy it, a double bond is used between the
two carbon atoms
...


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Electron dot structure of ethene
H
C

H

Science Class 10th Term II

Isomerism

H
C

ne

H

(iii) Structure of Ethyne (C 2H2 )
[Step I]
C—C
[Step II and III]
H  C ≡≡ C  H
In ethyne, the two carbon atoms share three pairs of
electrons among themselves to form a carbon-carbon triple
bond
...

Electron dot structure of ethyne

Carbon compounds or organic compounds with same
molecular formula can show different structures and hence,
different properties
...

For example, following two arrangements are possible
for butane, an alkane with four C atoms (C 4 H10 )
H H H H
   
H C  C  C  C H
   
H H H H
Straight chain structure

H

H

C

C

H

H C

C

H H

How to Draw Structure of Cyclic
Compounds ?
Some carbon compounds also exist in cyclic or ring
structure
...

Step 2 Try to satisfy the tetravalancy of each carbon with
the available hydrogen atoms
...
If it is found
unsatisfied, use double or triple bond to satisfy it
...
Thus, chain isomers are
the compounds that have same molecular formula but differ
in the arrangement of carbon chains
...


Examples
Cyclohexane (C 6H12 )
H H H H
H
H

®

C——C
C

C
C——C

H
H

or

Functional Groups

H H H H

Benzene (C 6H 6 )
H
C
H

C

C

H

H

C

C

H

or
C
H

Chain and position isomerism is possible only when, atleast
4 carbon atoms are present in the hydrocarbons
...
These are called
hetero atoms
...
Hence,
these are called functional groups
...

Following steps are used to write the name of an organic
compound
Step 1 Count the number of carbon atoms in the given
compound and write the root word for it (Root
word upto 10 carbon atoms are tabulated below
...

Characteristics of a Homologous Series
q
All the members of a homologous series can be
represented by the same general formulae
...

q
All the compounds of a homologous series show similar
chemical properties
...

q
The 14 u is the difference in the molecular masses of any
two adjacent homologues
...


Step 3

Meth

6

(C 6

Hex

(C 2 )

Eth

7

(C 7 )

Hept

(C 3 )

Prop

8

(C 8 )

Oct

(C 4 )

But

9

(C 9 )

Non

5

Step 2

(C1 )

4

functional group

O


C

Root
word

3

Free valency or valencies of the functional group are shown by
the single line
...
of
C atoms

2

R—NO 2

The formula of a particular family is made up of two
parts
...
For example,
CH
OH
→ Methanol or methyl alcohol
4
3
1 23 3 14 244
4 4

Root word

1

R—X

Halogen

—NO 2
®

No
...

For example, CH3 CH 2CH3 contains three C atoms
so root word is ‘prop’ and it contains only single
bonds, so suffix used is ‘ane’
...

Similarly, the compound CH3 CH == CH 2 is
named as propene as here suffix ‘ene’ is used for
double bond
...


Prefix and Suffix of Different Functional Groups
Functional
Group

Prefix/Suffix

Example

Alcohol

Suffix -ol

C 3H7 OH – Proane–e+ol
Propanol

Aldehyde

Suffix -al

CH3CHO – Ethane–e+al=
Ethanal

Ketone

Suffix -one

CH3COCH3 - Propane–e+one
Propanone

Carboxylic
acid

Suffix -oic acid

CH3COOH - Acetic acid/
Ethanoic acid

Halogen

Prefix -chloro,
bromo, etc
...

® If the functional group is named as a suffix, the final
‘e’ of alkane (or alkene or alkyne) is substituted by
appropriate suffix
...

®

Check

oint

2

1
...
Heat and light are also released during this process
...

CH 4 + 2 O 2 → CO 2 + 2H 2O + Heat + Light
Further, once carbon and its compounds ignite, they keep on burning
without the requirement of additional energy
...

Saturated hydrocarbons give a clean flame due to their complete
combustion whereas, unsaturated hydrocarbons give a yellow flame with
lots of black smoke as they do not undergo complete combustion
...
Reagents used for this purpose are alkaline KMnO 4 + heat or
acidified K 2Cr2O 7 + heat
...


3
...

4
...


compounds

(i) CH 3CH2CH2COOH
H

(ii) H  C  C ==O
 
H H
(iii) CH 3 −− OH
5
...

(i) CH 3OH
Cl

(ii) CH 3  C HCH 3
(iii) Ethanal
(iv) Acetic acid
(v) Hexyne

or Acidified K 2Cr2O 7
acetic acid
+ heat
(ethanoic acid)

ethanol

having five carbon atoms?

the

following

Science Class 10th Term II

Chemical Properties of Carbon Compounds

propene (C 3H6 )
...
What is the formula of an alkyne

ne

[O]

[O]

Alcohol → Aldehyde → Acid
...

For example, addition of hydrogen (in the presence of catalysts like
Palladium or Nickel) to unsaturated hydrocarbons, yields saturated
hydrocarbons (Hydrogenation)
...
This process is called hardening of oils
...

® Saturated fatty acids are harmful for health
...
This is
known as test of unsaturation
...
These are generally shown by saturated
compounds and benzene
...
So, presence of sunlight
is necessary for their substitution reactions
...


A flame is the region where combustion
(or burning) of gaseous substances takes place
...
The released energy (heat or
light) is utilised for various purposes like for cooking food, running
machines in factories, etc
...

Those fuels which were formed by the decomposition of the
remains of the pre-historic plants and animals (fossils) burried under
the earth long ago, are called fossils fuels
...

Coal
It is a complex mixture of compounds of carbon, hydrogen and
oxygen and some free carbon alongwith traces of nitrogen and
sulphur
...

Petroleum
It is a dark viscous foul smelling oil and is also known as rock oil
or black gold
...

®

Since coal and petroleum have nitrogen and sulphur in small amounts
that’s why they play an important role in causing pollution (air pollution)
...
Since, light
is not produced during this type of combustion, so
the flame is called non-luminous (non-light giving
flame), e
...
, burning of LPG in gas stove
...
The colour
of the flame is yellow because of the presence of
unburnt carbon particles
...
e
...
, burning of
wax vapours
...
Such fuels burn without producing
a flame
...


Some Important Carbon
Compounds
Ethanol
Its common name is ethyl alcohol and formula is
C 2H5 OH
...

yeast

Sugar → Molasses   → Ethanol
...
Its melting
point is 156 K and boiling point is 351 K
...


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acetic acid (a carboxylic acid), a fruity (sweet)
smelling liquid called ester, is obtained
...


2Na + 2CH3 CH 2 OH → 2CH3 CH 2 O Na + H 2
–

+

(Sodium ethoxide)

Acid

(ii) Dehydration (Removal of water) it is done by

CH3 COOH + CH3 CH 2OH →

conc
...


Ethanoic
acid

hot concentrated

CH3  CH 2OH → CH 2 ==CH 2 + H 2O
Ethanol

H2SO 4
160°C

Science Class 10th Term II

(ii) Esterification When ethanol (an alcohol) reacts with

Chemical Reactions
(i) With sodium Hydrogen is evolved
Sodium

ne

Ethanol

CH3 C  O  CH 2CH3


O

Ethene

Uses
Uses of ethanol are
q
It is used as active ingredients in all alcoholic drinks
...

q
Alcohol is used as an additive in petrol, since it is a
cleaner fuel and gives rise to only CO 2 and H 2O
...

q
It is used for the preparation of chloroform, iodoform,
ethanoic acid, ethanal, etc
...

This reaction is called saponification, as it is used for the
preparation of soap
...
It is an example of
acid base reaction
...
Its formula is
CH3 COOH
...

Physical Properties
Physical properties of ethanoic acid are
q
Its melting point is 290 K
...

Chemical Reactions
(i) Acidity It is a weaker acid than HCl but stronger
than alcohol
...

2CH3 COOH + 2Na → 2CH3 COONa + H 2

Esters are used in making perfumes and as flavouring agents
...

(ii) It is used in making pickles
...


Soaps and Detergents
Soaps are sodium or potassium salts of long chain
carboxylic acids and have general formula RCOONa
...


C 15 H31COOH is called palmitic acid
...

Manufacture of Soap and Detergents
Soaps are made from animal fat or vegetable oils by
heating it with sodium hydroxide
...
Hence, the dirt suspended in the
micelles is also easily rinsed away
...

In case of detergents, the long chain hydrocarbons obtained
from petroleum is taken instead of fat or oil
...


Structure of a Soap Molecule
A soap molecule is made up of two parts—a long hydrocarbon
part and a short ionic part containing – COONa group
...
The ionic portion of the soap molecule is
hydrophilic so soluble in water and insoluble in oil
...

At the surface of water, the hydrophobic end or ‘tail’ of soap
will be insoluble in water and the soap will lie along the surface of
water with the ionic end in water and the hydrocarbon ‘tail’
protruding out of water
...
This is done by
forming clusters of molecules in which the hydrophobic tails are
in the interior of the cluster and on the surface of cluster, ionic
ends are present
...
To
wash away the loosened dirt particles in the form of micelles from
the surface of the cloth, it is either scrubbed mechanically or
beaten or agitated in washing machine
...
Micelles stays as colloids
in the solution and does not come closer to precipitate due to

Cleaning Action of Soap (Micelle formation)

Soap forms scum with hard water as it reacts with
calcium and magnesium ions present in the hard water
...

Hence, they are effective in hard water
...

Detergents are useful in making shampoos and
products for cleaning clothes but their main disadvantage
is that these are generally non-biodegradable
...

q
Synthetic detergents can be used with hard water
while soaps cannot be used with hard water
...


Check

oint

3

1
...

3
...

5
...


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Answers for Check Points
Check Point
1
...

3
...


5
...


H

C

C

C

If n = 5
The formula of alkyne is C 5H2 × 5 − 2 = C 5H10 − 2 = C 5H8
...


(i) Butanoic acid
(ii) Ethanal
(iii) Methanol
(i) Alcohol
(ii) Chloro
(iii) Aldehyde
(iv) Carboxylic acid
(v) Triple bond (alkyne)
...


C

2,2-dimethyl propane or neo-pentane

H

3
...


H

CH

C

H

2

H

H

H
H

HC

Although graphite is a covalent molecule but its each carbon
atom utilise only three electrons for bonding and the fourth
electron of each carbon atom is free which makes it good
conductor of electricity
...


C

H

Because of the absence of free ions or electrons
...


H

(iii)

3

Check Point
1
...


Nickel

3
...


3

Because of their sweet smell
...


Because these are inert and sunlight generates free radicals
which readily attacks on alkanes

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