Textbook: Carbon Compounds | Science and Technology Class 10 (Maharashtra SSC Board) PDF Download

 Page 1


110
 1. What are the types of compounds ?
 In the previous standards we have seen that organic and inorganic compounds are the 
two important types of compounds.  Except materials fabricated from metal and glass/soil 
several other materials from foodstuff to fuels are made up of organic compounds. The 
essential element in all the organic compounds is carbon. About 200 years back it was 
believed that organic compounds are obtained directly or indirectly from the organisms. 
However, after synthesis of the organic compound urea from an inorganic compounds in the 
laboratory, the organic compounds received a new identity as carbon compounds. All the 
compounds having carbon as a constituent element are called as organic compounds. The 
compounds carbon dioxide, carbon monoxide, carbide salts, carbonate salts and bicarbonate 
salts are exception; they are inorganic compounds of carbon.
Bonds in Carbon compounds
 You have learnt about the ionic compounds in the previous chapter. You have seen that 
ionic compounds have high melting and boiling points and they conduct electricity in the molten 
and dissolved state. You have also seen that these properties of ionic compounds are explained 
on the basis of the ionic bonds in them. The table 9.1 shows melting and boiling points of a few 
carbon compounds. Are these values higher or lower as compared to the ionic compounds?
1. What is meant by a chemical bond?
2. What is the number of chemical bonds that an 
atom of an element forms called? 
3. What are the two important types of chemical 
bonds?
Ø  Bonds in carbon compounds                     Ø    Carbon : A Versatile Element
Ø  Hydrocarbons, Functional Groups and           Ø 	Nomenclature of Carbon      
      homologous series           compounds      
Ø  Chemical Properties of Carbon Compounds  Ø 	Macromolecules and Polymers
9. Carbon Compounds
2.  Objects in everyday use such as foodstuff, fibers, paper, medicines, wood, fuels, are made 
of various compounds. Which constituent elements are common in these compounds?
3.  To which group in the periodic table does the element carbon belongs ? Write down the 
electronic configuration of carbon and deduce the valency of carbon.
Compound
Melting point 
0
C
Boiling point 
0
C
Methane (CH
4
)
Ethanol (CH
3
CH
2
OH)
Chloroform (CHCl
3
)
Acetic acid (CH
3
COOH)
- 183
- 117
- 64
   17
- 162
   78
   61
   118
 Generally the melting and boiling 
points of carbon compounds are found to 
be lower than 300 
0
C. From this we 
understood that the intermolecular 
attractive forces are weak in carbon 
compounds.
 In the previous standard on testing 
the electrical conductivity of carbon 
compounds, glucose and urea you have 
observed that they   are not electrical 
conductors.  Generally most of the carbon 
compounds are found to be bad conductors 
of electricity. From it we understand that 
structures of most of the carbon compounds 
lack ionic bonds. It means that the 
chemical bonds in carbon compounds do 
not produce ions.
9.1 Melting and Boiling Points of a few carbon 
compounds
Can you recall?
Can you tell?
Page 2


110
 1. What are the types of compounds ?
 In the previous standards we have seen that organic and inorganic compounds are the 
two important types of compounds.  Except materials fabricated from metal and glass/soil 
several other materials from foodstuff to fuels are made up of organic compounds. The 
essential element in all the organic compounds is carbon. About 200 years back it was 
believed that organic compounds are obtained directly or indirectly from the organisms. 
However, after synthesis of the organic compound urea from an inorganic compounds in the 
laboratory, the organic compounds received a new identity as carbon compounds. All the 
compounds having carbon as a constituent element are called as organic compounds. The 
compounds carbon dioxide, carbon monoxide, carbide salts, carbonate salts and bicarbonate 
salts are exception; they are inorganic compounds of carbon.
Bonds in Carbon compounds
 You have learnt about the ionic compounds in the previous chapter. You have seen that 
ionic compounds have high melting and boiling points and they conduct electricity in the molten 
and dissolved state. You have also seen that these properties of ionic compounds are explained 
on the basis of the ionic bonds in them. The table 9.1 shows melting and boiling points of a few 
carbon compounds. Are these values higher or lower as compared to the ionic compounds?
1. What is meant by a chemical bond?
2. What is the number of chemical bonds that an 
atom of an element forms called? 
3. What are the two important types of chemical 
bonds?
Ø  Bonds in carbon compounds                     Ø    Carbon : A Versatile Element
Ø  Hydrocarbons, Functional Groups and           Ø 	Nomenclature of Carbon      
      homologous series           compounds      
Ø  Chemical Properties of Carbon Compounds  Ø 	Macromolecules and Polymers
9. Carbon Compounds
2.  Objects in everyday use such as foodstuff, fibers, paper, medicines, wood, fuels, are made 
of various compounds. Which constituent elements are common in these compounds?
3.  To which group in the periodic table does the element carbon belongs ? Write down the 
electronic configuration of carbon and deduce the valency of carbon.
Compound
Melting point 
0
C
Boiling point 
0
C
Methane (CH
4
)
Ethanol (CH
3
CH
2
OH)
Chloroform (CHCl
3
)
Acetic acid (CH
3
COOH)
- 183
- 117
- 64
   17
- 162
   78
   61
   118
 Generally the melting and boiling 
points of carbon compounds are found to 
be lower than 300 
0
C. From this we 
understood that the intermolecular 
attractive forces are weak in carbon 
compounds.
 In the previous standard on testing 
the electrical conductivity of carbon 
compounds, glucose and urea you have 
observed that they   are not electrical 
conductors.  Generally most of the carbon 
compounds are found to be bad conductors 
of electricity. From it we understand that 
structures of most of the carbon compounds 
lack ionic bonds. It means that the 
chemical bonds in carbon compounds do 
not produce ions.
9.1 Melting and Boiling Points of a few carbon 
compounds
Can you recall?
Can you tell?
111
 In the previous standards you have learnt about the relationship between electronic 
configuration and valency of an element, and also about the ionic and covalent bonds. Let see 
at the background of electronic configuration of carbon and the covalent bonds formed. (See 
Table 9.2).
9.2 Background of bond formation by carbon
Carbon 
atom
Electronic 
Configuration 
Number of electron in the 
Valence shell
Most nearby noble gas and the  
electronic configuration
He Ne
6
C 2, 4 4 2 2,8
 You have seen that the driving force behind the formation of bond by an atom is to attain 
the stable electronic configuration of the nearby noble gas and obtain stability. As the valence 
shell of carbon contains 4 electrons, there can be many alternative routes to attain a noble gas 
configuration.
 (i) To attain the configuration of noble gas helium (He) by losing one after another all the 
four valence electrons : In this method the net positive charge on the carbon atom goes on 
increasing during loss of every electrons. Therefore to lose the next electron more energy is 
required, which makes the task more difficult. Moreover, the  C
4+ 
cation that would ultimately 
form in this process becomes unstable in spite of its noble gas configuration, because it has a 
small size with high net charge. Therefore carbon atom does not take this route to attain a 
noble gas configuration.
 (ii) To attain the stable configuration of the noble gas neon (Ne) by accepting one by one 
ass the four electrons in the valence shell.  In this method the net negative charge on the 
carbon atom goes on increasing while accepting every new electron. Therefore, more energy 
is required for accepting the next electron by overcoming the increasing repulsive force making 
the task more and more difficult. Moreover the C
4-
  anion ultimately formed would be unstable 
in spite of its noble gas configuration, as it would have a small size with high net charge 
making it difficult for the nuclear charge +6 to hold 10 electrons around it. Therefore, carbon 
atom does not take this route to attain a noble gas configuration.
 (iii) To attain the configuration of neon by sharing four electrons of valence shell with 
four valence electrons of other atoms: In this method two atoms share valence electrons with 
each other. Valence shells of both the atoms overlap and accommodate the shared electrons, 
As a result, both the atoms attain a noble gas configuration without generating any net charge 
on them, which means that atoms remain electrically neutral. Due to these factors atoms 
attain stability. Therefore, carbon atom adopts this route to attain a noble gas configuration.
 The chemical bond formed by sharing of two valence electrons between the two atoms is 
called covalent bond.
  A covalent bond is represented clearly by drawing an electron - dot structure. In this 
method a circle is drawn around the atomic symbol and each of the valence electrons is 
indicated by a dot or a cross. The covalent bond formed between the atoms is indicated by 
showing the circles around the atomic symbols crossing each other. The shared electrons are 
shown in the overlapping regions of the two circles by dot or cross. The electron - dot structure 
is also drawn without showing the circle. One pair of shared electrons constitutes one covalent 
bond . A covalent bond is also represented by a small line joining the symbols of the two 
atoms. The line structure  is also called structural formula.  
Single bond
9.3 Electron dot structure and line structure of hydrogen molecule with a single bond
H : H
Page 3


110
 1. What are the types of compounds ?
 In the previous standards we have seen that organic and inorganic compounds are the 
two important types of compounds.  Except materials fabricated from metal and glass/soil 
several other materials from foodstuff to fuels are made up of organic compounds. The 
essential element in all the organic compounds is carbon. About 200 years back it was 
believed that organic compounds are obtained directly or indirectly from the organisms. 
However, after synthesis of the organic compound urea from an inorganic compounds in the 
laboratory, the organic compounds received a new identity as carbon compounds. All the 
compounds having carbon as a constituent element are called as organic compounds. The 
compounds carbon dioxide, carbon monoxide, carbide salts, carbonate salts and bicarbonate 
salts are exception; they are inorganic compounds of carbon.
Bonds in Carbon compounds
 You have learnt about the ionic compounds in the previous chapter. You have seen that 
ionic compounds have high melting and boiling points and they conduct electricity in the molten 
and dissolved state. You have also seen that these properties of ionic compounds are explained 
on the basis of the ionic bonds in them. The table 9.1 shows melting and boiling points of a few 
carbon compounds. Are these values higher or lower as compared to the ionic compounds?
1. What is meant by a chemical bond?
2. What is the number of chemical bonds that an 
atom of an element forms called? 
3. What are the two important types of chemical 
bonds?
Ø  Bonds in carbon compounds                     Ø    Carbon : A Versatile Element
Ø  Hydrocarbons, Functional Groups and           Ø 	Nomenclature of Carbon      
      homologous series           compounds      
Ø  Chemical Properties of Carbon Compounds  Ø 	Macromolecules and Polymers
9. Carbon Compounds
2.  Objects in everyday use such as foodstuff, fibers, paper, medicines, wood, fuels, are made 
of various compounds. Which constituent elements are common in these compounds?
3.  To which group in the periodic table does the element carbon belongs ? Write down the 
electronic configuration of carbon and deduce the valency of carbon.
Compound
Melting point 
0
C
Boiling point 
0
C
Methane (CH
4
)
Ethanol (CH
3
CH
2
OH)
Chloroform (CHCl
3
)
Acetic acid (CH
3
COOH)
- 183
- 117
- 64
   17
- 162
   78
   61
   118
 Generally the melting and boiling 
points of carbon compounds are found to 
be lower than 300 
0
C. From this we 
understood that the intermolecular 
attractive forces are weak in carbon 
compounds.
 In the previous standard on testing 
the electrical conductivity of carbon 
compounds, glucose and urea you have 
observed that they   are not electrical 
conductors.  Generally most of the carbon 
compounds are found to be bad conductors 
of electricity. From it we understand that 
structures of most of the carbon compounds 
lack ionic bonds. It means that the 
chemical bonds in carbon compounds do 
not produce ions.
9.1 Melting and Boiling Points of a few carbon 
compounds
Can you recall?
Can you tell?
111
 In the previous standards you have learnt about the relationship between electronic 
configuration and valency of an element, and also about the ionic and covalent bonds. Let see 
at the background of electronic configuration of carbon and the covalent bonds formed. (See 
Table 9.2).
9.2 Background of bond formation by carbon
Carbon 
atom
Electronic 
Configuration 
Number of electron in the 
Valence shell
Most nearby noble gas and the  
electronic configuration
He Ne
6
C 2, 4 4 2 2,8
 You have seen that the driving force behind the formation of bond by an atom is to attain 
the stable electronic configuration of the nearby noble gas and obtain stability. As the valence 
shell of carbon contains 4 electrons, there can be many alternative routes to attain a noble gas 
configuration.
 (i) To attain the configuration of noble gas helium (He) by losing one after another all the 
four valence electrons : In this method the net positive charge on the carbon atom goes on 
increasing during loss of every electrons. Therefore to lose the next electron more energy is 
required, which makes the task more difficult. Moreover, the  C
4+ 
cation that would ultimately 
form in this process becomes unstable in spite of its noble gas configuration, because it has a 
small size with high net charge. Therefore carbon atom does not take this route to attain a 
noble gas configuration.
 (ii) To attain the stable configuration of the noble gas neon (Ne) by accepting one by one 
ass the four electrons in the valence shell.  In this method the net negative charge on the 
carbon atom goes on increasing while accepting every new electron. Therefore, more energy 
is required for accepting the next electron by overcoming the increasing repulsive force making 
the task more and more difficult. Moreover the C
4-
  anion ultimately formed would be unstable 
in spite of its noble gas configuration, as it would have a small size with high net charge 
making it difficult for the nuclear charge +6 to hold 10 electrons around it. Therefore, carbon 
atom does not take this route to attain a noble gas configuration.
 (iii) To attain the configuration of neon by sharing four electrons of valence shell with 
four valence electrons of other atoms: In this method two atoms share valence electrons with 
each other. Valence shells of both the atoms overlap and accommodate the shared electrons, 
As a result, both the atoms attain a noble gas configuration without generating any net charge 
on them, which means that atoms remain electrically neutral. Due to these factors atoms 
attain stability. Therefore, carbon atom adopts this route to attain a noble gas configuration.
 The chemical bond formed by sharing of two valence electrons between the two atoms is 
called covalent bond.
  A covalent bond is represented clearly by drawing an electron - dot structure. In this 
method a circle is drawn around the atomic symbol and each of the valence electrons is 
indicated by a dot or a cross. The covalent bond formed between the atoms is indicated by 
showing the circles around the atomic symbols crossing each other. The shared electrons are 
shown in the overlapping regions of the two circles by dot or cross. The electron - dot structure 
is also drawn without showing the circle. One pair of shared electrons constitutes one covalent 
bond . A covalent bond is also represented by a small line joining the symbols of the two 
atoms. The line structure  is also called structural formula.  
Single bond
9.3 Electron dot structure and line structure of hydrogen molecule with a single bond
H : H
112
 Let us first look at the hydrogen molecule which is the simplest example of a molecule 
formed by covalent bonding. You have already learnt that the atomic number of hydrogen 
being 1, its atom contains 1 electron in K shell. It requires one more electron to complete the 
K shell and attain the configuration  of helium (He). To meet this requirement two hydrogen 
atoms share their electrons with each other to form H
2
 molecule. One covalent bond, that is a 
single bond is formed between two hydrogen atoms by sharing of two electrons. (see fig 9.3).
 The O
2
 molecule is formed by chemical combination of two oxygen atoms;  and N
2 
molecule is formed by the chemical combination of two nitrogen atoms. On drawing the  
electron-dot structures of these two molecules, it becomes clear that the two oxygen atoms in 
O
2 
molecule are joined with each other by two covalent bonds, that is, a double bond, while 
the two nitrogen atoms in the N
2 
molecule are joined with each other by three covalent bonds, 
that is, a triple bond (See figure 9.4) (Remember that it is esseantial to show all the valance 
electrons in an electron dot structure.)
 Now let us consider a carbon compound 
methane (CH
4
). You have learnt about the 
occurrence, properties and uses of methane  
molecule in the previous standard. Just now we 
saw that carbon atom forms four covalent bonds 
using the four valence electrons and attain the 
configuration of the nearby noble gas neon (Ne) 
and obtains stability: Fig 9.5 shows the line 
structure and also the electron-dot structure of 
methane. 
1.  Atomic number of chlorine is 17.
 What is the number of electron in the 
valence shell of chlorine?
2. Molecular formula of chlorine is Cl
2
. 
Draw electron-dot and line structure of 
a chlorine molecule.
3. The molecular formula of water is H
2
O. 
Draw electron-dot and line structures 
for this triatomic molecule. (Use dots 
for electron of oxygen atom and 
crosses for electrons of hydrogen 
atoms.)
4. The molecular formula of ammonia is 
NH
3
. Draw electron-dot and line 
structures for ammonia molecule.
9.4 Double Bond and Triple Bond
Two atoms of 
oxygen
triple bond
double bond
 To understand the structures of carbon 
compounds various types of molecular 
models are used. The fig 9.6 shows ball and 
stick model and space filling model of 
methane molecule.
Do you know ?
1. The molecular formula of carbon dioxide is CO
2
. Draw the electron-dot structure (without 
showing circle) and line structure for CO
2
.
2. With which bond C atom in CO
2 
is bonded to each of the O atoms?
3. The molecular formula of sulphur is S
8
 in which eight sulphur atoms are bonded to each 
other to form one ring. Draw an electron-dot structure for S
8
 without showing the circles.
Use your brain power !
Use your brain power !
. . . .
. .
. .
: :
:
:
:
:
Page 4


110
 1. What are the types of compounds ?
 In the previous standards we have seen that organic and inorganic compounds are the 
two important types of compounds.  Except materials fabricated from metal and glass/soil 
several other materials from foodstuff to fuels are made up of organic compounds. The 
essential element in all the organic compounds is carbon. About 200 years back it was 
believed that organic compounds are obtained directly or indirectly from the organisms. 
However, after synthesis of the organic compound urea from an inorganic compounds in the 
laboratory, the organic compounds received a new identity as carbon compounds. All the 
compounds having carbon as a constituent element are called as organic compounds. The 
compounds carbon dioxide, carbon monoxide, carbide salts, carbonate salts and bicarbonate 
salts are exception; they are inorganic compounds of carbon.
Bonds in Carbon compounds
 You have learnt about the ionic compounds in the previous chapter. You have seen that 
ionic compounds have high melting and boiling points and they conduct electricity in the molten 
and dissolved state. You have also seen that these properties of ionic compounds are explained 
on the basis of the ionic bonds in them. The table 9.1 shows melting and boiling points of a few 
carbon compounds. Are these values higher or lower as compared to the ionic compounds?
1. What is meant by a chemical bond?
2. What is the number of chemical bonds that an 
atom of an element forms called? 
3. What are the two important types of chemical 
bonds?
Ø  Bonds in carbon compounds                     Ø    Carbon : A Versatile Element
Ø  Hydrocarbons, Functional Groups and           Ø 	Nomenclature of Carbon      
      homologous series           compounds      
Ø  Chemical Properties of Carbon Compounds  Ø 	Macromolecules and Polymers
9. Carbon Compounds
2.  Objects in everyday use such as foodstuff, fibers, paper, medicines, wood, fuels, are made 
of various compounds. Which constituent elements are common in these compounds?
3.  To which group in the periodic table does the element carbon belongs ? Write down the 
electronic configuration of carbon and deduce the valency of carbon.
Compound
Melting point 
0
C
Boiling point 
0
C
Methane (CH
4
)
Ethanol (CH
3
CH
2
OH)
Chloroform (CHCl
3
)
Acetic acid (CH
3
COOH)
- 183
- 117
- 64
   17
- 162
   78
   61
   118
 Generally the melting and boiling 
points of carbon compounds are found to 
be lower than 300 
0
C. From this we 
understood that the intermolecular 
attractive forces are weak in carbon 
compounds.
 In the previous standard on testing 
the electrical conductivity of carbon 
compounds, glucose and urea you have 
observed that they   are not electrical 
conductors.  Generally most of the carbon 
compounds are found to be bad conductors 
of electricity. From it we understand that 
structures of most of the carbon compounds 
lack ionic bonds. It means that the 
chemical bonds in carbon compounds do 
not produce ions.
9.1 Melting and Boiling Points of a few carbon 
compounds
Can you recall?
Can you tell?
111
 In the previous standards you have learnt about the relationship between electronic 
configuration and valency of an element, and also about the ionic and covalent bonds. Let see 
at the background of electronic configuration of carbon and the covalent bonds formed. (See 
Table 9.2).
9.2 Background of bond formation by carbon
Carbon 
atom
Electronic 
Configuration 
Number of electron in the 
Valence shell
Most nearby noble gas and the  
electronic configuration
He Ne
6
C 2, 4 4 2 2,8
 You have seen that the driving force behind the formation of bond by an atom is to attain 
the stable electronic configuration of the nearby noble gas and obtain stability. As the valence 
shell of carbon contains 4 electrons, there can be many alternative routes to attain a noble gas 
configuration.
 (i) To attain the configuration of noble gas helium (He) by losing one after another all the 
four valence electrons : In this method the net positive charge on the carbon atom goes on 
increasing during loss of every electrons. Therefore to lose the next electron more energy is 
required, which makes the task more difficult. Moreover, the  C
4+ 
cation that would ultimately 
form in this process becomes unstable in spite of its noble gas configuration, because it has a 
small size with high net charge. Therefore carbon atom does not take this route to attain a 
noble gas configuration.
 (ii) To attain the stable configuration of the noble gas neon (Ne) by accepting one by one 
ass the four electrons in the valence shell.  In this method the net negative charge on the 
carbon atom goes on increasing while accepting every new electron. Therefore, more energy 
is required for accepting the next electron by overcoming the increasing repulsive force making 
the task more and more difficult. Moreover the C
4-
  anion ultimately formed would be unstable 
in spite of its noble gas configuration, as it would have a small size with high net charge 
making it difficult for the nuclear charge +6 to hold 10 electrons around it. Therefore, carbon 
atom does not take this route to attain a noble gas configuration.
 (iii) To attain the configuration of neon by sharing four electrons of valence shell with 
four valence electrons of other atoms: In this method two atoms share valence electrons with 
each other. Valence shells of both the atoms overlap and accommodate the shared electrons, 
As a result, both the atoms attain a noble gas configuration without generating any net charge 
on them, which means that atoms remain electrically neutral. Due to these factors atoms 
attain stability. Therefore, carbon atom adopts this route to attain a noble gas configuration.
 The chemical bond formed by sharing of two valence electrons between the two atoms is 
called covalent bond.
  A covalent bond is represented clearly by drawing an electron - dot structure. In this 
method a circle is drawn around the atomic symbol and each of the valence electrons is 
indicated by a dot or a cross. The covalent bond formed between the atoms is indicated by 
showing the circles around the atomic symbols crossing each other. The shared electrons are 
shown in the overlapping regions of the two circles by dot or cross. The electron - dot structure 
is also drawn without showing the circle. One pair of shared electrons constitutes one covalent 
bond . A covalent bond is also represented by a small line joining the symbols of the two 
atoms. The line structure  is also called structural formula.  
Single bond
9.3 Electron dot structure and line structure of hydrogen molecule with a single bond
H : H
112
 Let us first look at the hydrogen molecule which is the simplest example of a molecule 
formed by covalent bonding. You have already learnt that the atomic number of hydrogen 
being 1, its atom contains 1 electron in K shell. It requires one more electron to complete the 
K shell and attain the configuration  of helium (He). To meet this requirement two hydrogen 
atoms share their electrons with each other to form H
2
 molecule. One covalent bond, that is a 
single bond is formed between two hydrogen atoms by sharing of two electrons. (see fig 9.3).
 The O
2
 molecule is formed by chemical combination of two oxygen atoms;  and N
2 
molecule is formed by the chemical combination of two nitrogen atoms. On drawing the  
electron-dot structures of these two molecules, it becomes clear that the two oxygen atoms in 
O
2 
molecule are joined with each other by two covalent bonds, that is, a double bond, while 
the two nitrogen atoms in the N
2 
molecule are joined with each other by three covalent bonds, 
that is, a triple bond (See figure 9.4) (Remember that it is esseantial to show all the valance 
electrons in an electron dot structure.)
 Now let us consider a carbon compound 
methane (CH
4
). You have learnt about the 
occurrence, properties and uses of methane  
molecule in the previous standard. Just now we 
saw that carbon atom forms four covalent bonds 
using the four valence electrons and attain the 
configuration of the nearby noble gas neon (Ne) 
and obtains stability: Fig 9.5 shows the line 
structure and also the electron-dot structure of 
methane. 
1.  Atomic number of chlorine is 17.
 What is the number of electron in the 
valence shell of chlorine?
2. Molecular formula of chlorine is Cl
2
. 
Draw electron-dot and line structure of 
a chlorine molecule.
3. The molecular formula of water is H
2
O. 
Draw electron-dot and line structures 
for this triatomic molecule. (Use dots 
for electron of oxygen atom and 
crosses for electrons of hydrogen 
atoms.)
4. The molecular formula of ammonia is 
NH
3
. Draw electron-dot and line 
structures for ammonia molecule.
9.4 Double Bond and Triple Bond
Two atoms of 
oxygen
triple bond
double bond
 To understand the structures of carbon 
compounds various types of molecular 
models are used. The fig 9.6 shows ball and 
stick model and space filling model of 
methane molecule.
Do you know ?
1. The molecular formula of carbon dioxide is CO
2
. Draw the electron-dot structure (without 
showing circle) and line structure for CO
2
.
2. With which bond C atom in CO
2 
is bonded to each of the O atoms?
3. The molecular formula of sulphur is S
8
 in which eight sulphur atoms are bonded to each 
other to form one ring. Draw an electron-dot structure for S
8
 without showing the circles.
Use your brain power !
Use your brain power !
. . . .
. .
. .
: :
:
:
:
:
113
9.6 Models of methane molecule
methane 
molecule
four hydrogen 
atoms and one 
carbon atom covalent 
bond
9.5 Electron-dot structure and line structure of methane molecule
Carbon : A Versatile Element
 We saw that carbon atoms, like some 
other atoms, share the valence electrons to 
form covalent bonds. Similarly, we also 
saw the structure of the simple carbon 
compound, methane. But carbon is different 
than the other elements; the number of  
compounds formed from carbon is 
extremely large. In the beginning we saw 
that except for the objects formed from 
metals and glass/soil all the other objects 
are made from carbon. In short, brief the 
entire living kingdom is made from carbon, 
our body is also made from carbon. 
Millions of molecules ranging from the 
small and simple methane molecule to the 
extremely big D.N.A. molecule are made 
from carbon. The molecular masses of 
carbon compounds range up to 10
12
. This 
means that carbon atoms come together in 
a large number to form extremely big 
molecules. What is the cause of this unique 
property of carbon? It is due to the peculiar 
nature of the covalent bonds formed by 
carbon, it can form large number of 
compounds. From this we come to know 
the following characteristics of carbon.
a. Carbon has a unique ability to form 
strong covalent bonds with other carbon 
atoms; this results in formation of big 
molecules. This property of carbon is called 
catenation power. The carbon compounds 
contain open chains or closed  chains of 
carbon atoms. An open chain can be a 
straight chain or a branched chain. A closed 
chain is a ring structure. The covalent bond 
between two  carbon atoms is strong and 
therefore stable. Due to the strong and 
stable covalent bonds carbon is bestowed 
with catenation power.   
 Till now the number of known 
carbon compounds is about 10 
million. This number is larger than 
the total number of compounds 
formed by all the other elements. The 
range of molecular masses of carbon 
compounds is 10
1
 - 10
12
.
(See table 9.7)
Ball & stick 
model
Space filling model
1. Hydrogen peroxide decomposes 
on its own by the following 
reaction 
     H-O-O-H  2H-O-H + O
2
 
      From this, what will be your 
inference about the strength of 
O-O covalent bond?
2. Tell from the above example 
whether oxygen has catenation 
power or not.  
Use your brain power !
Page 5


110
 1. What are the types of compounds ?
 In the previous standards we have seen that organic and inorganic compounds are the 
two important types of compounds.  Except materials fabricated from metal and glass/soil 
several other materials from foodstuff to fuels are made up of organic compounds. The 
essential element in all the organic compounds is carbon. About 200 years back it was 
believed that organic compounds are obtained directly or indirectly from the organisms. 
However, after synthesis of the organic compound urea from an inorganic compounds in the 
laboratory, the organic compounds received a new identity as carbon compounds. All the 
compounds having carbon as a constituent element are called as organic compounds. The 
compounds carbon dioxide, carbon monoxide, carbide salts, carbonate salts and bicarbonate 
salts are exception; they are inorganic compounds of carbon.
Bonds in Carbon compounds
 You have learnt about the ionic compounds in the previous chapter. You have seen that 
ionic compounds have high melting and boiling points and they conduct electricity in the molten 
and dissolved state. You have also seen that these properties of ionic compounds are explained 
on the basis of the ionic bonds in them. The table 9.1 shows melting and boiling points of a few 
carbon compounds. Are these values higher or lower as compared to the ionic compounds?
1. What is meant by a chemical bond?
2. What is the number of chemical bonds that an 
atom of an element forms called? 
3. What are the two important types of chemical 
bonds?
Ø  Bonds in carbon compounds                     Ø    Carbon : A Versatile Element
Ø  Hydrocarbons, Functional Groups and           Ø 	Nomenclature of Carbon      
      homologous series           compounds      
Ø  Chemical Properties of Carbon Compounds  Ø 	Macromolecules and Polymers
9. Carbon Compounds
2.  Objects in everyday use such as foodstuff, fibers, paper, medicines, wood, fuels, are made 
of various compounds. Which constituent elements are common in these compounds?
3.  To which group in the periodic table does the element carbon belongs ? Write down the 
electronic configuration of carbon and deduce the valency of carbon.
Compound
Melting point 
0
C
Boiling point 
0
C
Methane (CH
4
)
Ethanol (CH
3
CH
2
OH)
Chloroform (CHCl
3
)
Acetic acid (CH
3
COOH)
- 183
- 117
- 64
   17
- 162
   78
   61
   118
 Generally the melting and boiling 
points of carbon compounds are found to 
be lower than 300 
0
C. From this we 
understood that the intermolecular 
attractive forces are weak in carbon 
compounds.
 In the previous standard on testing 
the electrical conductivity of carbon 
compounds, glucose and urea you have 
observed that they   are not electrical 
conductors.  Generally most of the carbon 
compounds are found to be bad conductors 
of electricity. From it we understand that 
structures of most of the carbon compounds 
lack ionic bonds. It means that the 
chemical bonds in carbon compounds do 
not produce ions.
9.1 Melting and Boiling Points of a few carbon 
compounds
Can you recall?
Can you tell?
111
 In the previous standards you have learnt about the relationship between electronic 
configuration and valency of an element, and also about the ionic and covalent bonds. Let see 
at the background of electronic configuration of carbon and the covalent bonds formed. (See 
Table 9.2).
9.2 Background of bond formation by carbon
Carbon 
atom
Electronic 
Configuration 
Number of electron in the 
Valence shell
Most nearby noble gas and the  
electronic configuration
He Ne
6
C 2, 4 4 2 2,8
 You have seen that the driving force behind the formation of bond by an atom is to attain 
the stable electronic configuration of the nearby noble gas and obtain stability. As the valence 
shell of carbon contains 4 electrons, there can be many alternative routes to attain a noble gas 
configuration.
 (i) To attain the configuration of noble gas helium (He) by losing one after another all the 
four valence electrons : In this method the net positive charge on the carbon atom goes on 
increasing during loss of every electrons. Therefore to lose the next electron more energy is 
required, which makes the task more difficult. Moreover, the  C
4+ 
cation that would ultimately 
form in this process becomes unstable in spite of its noble gas configuration, because it has a 
small size with high net charge. Therefore carbon atom does not take this route to attain a 
noble gas configuration.
 (ii) To attain the stable configuration of the noble gas neon (Ne) by accepting one by one 
ass the four electrons in the valence shell.  In this method the net negative charge on the 
carbon atom goes on increasing while accepting every new electron. Therefore, more energy 
is required for accepting the next electron by overcoming the increasing repulsive force making 
the task more and more difficult. Moreover the C
4-
  anion ultimately formed would be unstable 
in spite of its noble gas configuration, as it would have a small size with high net charge 
making it difficult for the nuclear charge +6 to hold 10 electrons around it. Therefore, carbon 
atom does not take this route to attain a noble gas configuration.
 (iii) To attain the configuration of neon by sharing four electrons of valence shell with 
four valence electrons of other atoms: In this method two atoms share valence electrons with 
each other. Valence shells of both the atoms overlap and accommodate the shared electrons, 
As a result, both the atoms attain a noble gas configuration without generating any net charge 
on them, which means that atoms remain electrically neutral. Due to these factors atoms 
attain stability. Therefore, carbon atom adopts this route to attain a noble gas configuration.
 The chemical bond formed by sharing of two valence electrons between the two atoms is 
called covalent bond.
  A covalent bond is represented clearly by drawing an electron - dot structure. In this 
method a circle is drawn around the atomic symbol and each of the valence electrons is 
indicated by a dot or a cross. The covalent bond formed between the atoms is indicated by 
showing the circles around the atomic symbols crossing each other. The shared electrons are 
shown in the overlapping regions of the two circles by dot or cross. The electron - dot structure 
is also drawn without showing the circle. One pair of shared electrons constitutes one covalent 
bond . A covalent bond is also represented by a small line joining the symbols of the two 
atoms. The line structure  is also called structural formula.  
Single bond
9.3 Electron dot structure and line structure of hydrogen molecule with a single bond
H : H
112
 Let us first look at the hydrogen molecule which is the simplest example of a molecule 
formed by covalent bonding. You have already learnt that the atomic number of hydrogen 
being 1, its atom contains 1 electron in K shell. It requires one more electron to complete the 
K shell and attain the configuration  of helium (He). To meet this requirement two hydrogen 
atoms share their electrons with each other to form H
2
 molecule. One covalent bond, that is a 
single bond is formed between two hydrogen atoms by sharing of two electrons. (see fig 9.3).
 The O
2
 molecule is formed by chemical combination of two oxygen atoms;  and N
2 
molecule is formed by the chemical combination of two nitrogen atoms. On drawing the  
electron-dot structures of these two molecules, it becomes clear that the two oxygen atoms in 
O
2 
molecule are joined with each other by two covalent bonds, that is, a double bond, while 
the two nitrogen atoms in the N
2 
molecule are joined with each other by three covalent bonds, 
that is, a triple bond (See figure 9.4) (Remember that it is esseantial to show all the valance 
electrons in an electron dot structure.)
 Now let us consider a carbon compound 
methane (CH
4
). You have learnt about the 
occurrence, properties and uses of methane  
molecule in the previous standard. Just now we 
saw that carbon atom forms four covalent bonds 
using the four valence electrons and attain the 
configuration of the nearby noble gas neon (Ne) 
and obtains stability: Fig 9.5 shows the line 
structure and also the electron-dot structure of 
methane. 
1.  Atomic number of chlorine is 17.
 What is the number of electron in the 
valence shell of chlorine?
2. Molecular formula of chlorine is Cl
2
. 
Draw electron-dot and line structure of 
a chlorine molecule.
3. The molecular formula of water is H
2
O. 
Draw electron-dot and line structures 
for this triatomic molecule. (Use dots 
for electron of oxygen atom and 
crosses for electrons of hydrogen 
atoms.)
4. The molecular formula of ammonia is 
NH
3
. Draw electron-dot and line 
structures for ammonia molecule.
9.4 Double Bond and Triple Bond
Two atoms of 
oxygen
triple bond
double bond
 To understand the structures of carbon 
compounds various types of molecular 
models are used. The fig 9.6 shows ball and 
stick model and space filling model of 
methane molecule.
Do you know ?
1. The molecular formula of carbon dioxide is CO
2
. Draw the electron-dot structure (without 
showing circle) and line structure for CO
2
.
2. With which bond C atom in CO
2 
is bonded to each of the O atoms?
3. The molecular formula of sulphur is S
8
 in which eight sulphur atoms are bonded to each 
other to form one ring. Draw an electron-dot structure for S
8
 without showing the circles.
Use your brain power !
Use your brain power !
. . . .
. .
. .
: :
:
:
:
:
113
9.6 Models of methane molecule
methane 
molecule
four hydrogen 
atoms and one 
carbon atom covalent 
bond
9.5 Electron-dot structure and line structure of methane molecule
Carbon : A Versatile Element
 We saw that carbon atoms, like some 
other atoms, share the valence electrons to 
form covalent bonds. Similarly, we also 
saw the structure of the simple carbon 
compound, methane. But carbon is different 
than the other elements; the number of  
compounds formed from carbon is 
extremely large. In the beginning we saw 
that except for the objects formed from 
metals and glass/soil all the other objects 
are made from carbon. In short, brief the 
entire living kingdom is made from carbon, 
our body is also made from carbon. 
Millions of molecules ranging from the 
small and simple methane molecule to the 
extremely big D.N.A. molecule are made 
from carbon. The molecular masses of 
carbon compounds range up to 10
12
. This 
means that carbon atoms come together in 
a large number to form extremely big 
molecules. What is the cause of this unique 
property of carbon? It is due to the peculiar 
nature of the covalent bonds formed by 
carbon, it can form large number of 
compounds. From this we come to know 
the following characteristics of carbon.
a. Carbon has a unique ability to form 
strong covalent bonds with other carbon 
atoms; this results in formation of big 
molecules. This property of carbon is called 
catenation power. The carbon compounds 
contain open chains or closed  chains of 
carbon atoms. An open chain can be a 
straight chain or a branched chain. A closed 
chain is a ring structure. The covalent bond 
between two  carbon atoms is strong and 
therefore stable. Due to the strong and 
stable covalent bonds carbon is bestowed 
with catenation power.   
 Till now the number of known 
carbon compounds is about 10 
million. This number is larger than 
the total number of compounds 
formed by all the other elements. The 
range of molecular masses of carbon 
compounds is 10
1
 - 10
12
.
(See table 9.7)
Ball & stick 
model
Space filling model
1. Hydrogen peroxide decomposes 
on its own by the following 
reaction 
     H-O-O-H  2H-O-H + O
2
 
      From this, what will be your 
inference about the strength of 
O-O covalent bond?
2. Tell from the above example 
whether oxygen has catenation 
power or not.  
Use your brain power !
114
b. Two carbon atoms can be 
bonded together by one, two 
or three covalent bonds. 
These are called single bond, 
double bond, and triple bond 
respectively. Due to the 
ability of carbon atoms to 
form multiple bonds as well 
as single bonds, the number 
of carbon compounds 
increases. For example, 
there are three compounds, 
namely, ethane (CH
3
-CH
3
), 
ethene (CH
2
=CH
2
) and 
ethyne (CH º CH)  which 
contain two carbon atoms.
Carbon Compound                                Molecular mass
Methane CH
4 
(The smallest carbon compound)  16 
Cooking gas (C
3
H
8 
+ C
4 
H
10
)  44/58
Benzene ( C
6 
H
6
)  78
Camphor (C
10
H
16
O)  152
Penicillin (C
16
H
18
N
2
O
4
S)  334
Sugar (C
12
H
22
O
11)
  342
Sodium dodecyl benzene sulphate (a detergent) 347
Fat    ~ 700
Starch  ~ 10
3
Cellulose  ~ 10
5
Protein  ~ 10
5
Polyethylene  ~ 10
6
D.N.A.  ~ 10
12
9.7  Carbon compounds and molecular masses
9.8  Line structure / structural formula of ethane
c. Being tetravalent one carbon atom can form bonds with four other atoms (carbon or any 
other). This results in formation of many compounds. These compounds possess different 
properties as per the atoms to which carbon is bonded. For example, five different 
compounds are formed using one carbon atom and two monovalent elements hydrogen 
and chlorine : CH
4
, CH
3
Cl, CH
2
Cl
2
, CHCl
3
, CCl
4
. Similarly carbon atoms form covalent 
bonds with atoms of elements like O, N, S, halogen & P to form different types of carbon 
compounds in large number.
d. Carbon has one more characteristic which is responsible for large number of carbon 
compounds. It is ‘isomerism’. Shortly, we will learn about it.
Hydrocarbons : Saturated and Unsaturated
 Carbon compounds contain many elements. The element hydrogen is present to a 
smaller or larger extent in majority of carbon compounds. The compounds which contain 
carbon and hydrogen as the only two elements are called hydrocarbons. Hydrocarbons are 
the simplest and the fundamental organic compounds. The smallest hydrocarbon is 
methane (CH
4
) formed by combination of one carbon atom and four hydrogen atoms. We 
have already seen the structure of methane. Ethane is one more hydrocarbon. Its molecular 
formula is C
2
H
6
.  The first step in writing the line structure (structural formula) of a 
hydrocarbon is to join the carbon atoms in the molecule with single bonds, and then in the 
second step use the hydrogen atoms in the molecular formula so as to fulfil the remaining 
valencies of the  tetravalent carbon atoms. (See fig. 9.8), Fig. 9.9 shows electron-dot 
structure using two methods.
Ethane : Molecular formula C
2
H
6
Step 1 : Join the two carbon atoms with single bonds  C - C
Step 2 : Use the 6 hydrogen atoms in the molecular formula 
for fulfilling the tetravalency of both the carbon atoms.
9.9. Electron-dot structure of ethane