carbon and its compounds

carbon and its compounds

Class X 

1) Occurrence of carbon :-

i) Carbon is found in the atmosphere, inside the earth’s crust and in      all living organisms. 

 ii) Carbon is present in fuels like wood, coal, charcoal, coke, petroleum,      natural gas, biogas, marsh gas etc.

  iii) Carbon is present in compounds like carbonates,      hydrogen carbonates etc. 

iv) Carbon is found in the free state as diamond, graphite, fullerenes etc.

Bonding in carbon – Covalent bond :-

The atomic number of carbon is 6, its electronic arrangement is 2,4, it has 4 valence electrons. 

It can attain stability by gaining 4 electrons, losing 4 electrons or sharing 4 electrons with other atoms.     It does not gain 4 electrons because it is difficult for the 6 protons to hold 10 electrons.     

 It does not lose 4 electrons because it needs a large amount of energy to lose 4 electrons.    So it shares 4 electrons with other atoms to attain stability resulting in the formation of covalent bonds.    

 Since carbon atom needs 4 electrons to attain stability, its valency is 4 and it is tetravalent.

Multiple Choice

Carbon atoms gain stability by

• losing electrons

• gaining electrons

• forming covalent bonds

• forming ionic bonds

3) Formation of covalent bonds :-   

Covalent bond is chemical bond formed by the sharing of electrons between atoms. 

 The sharing of one pair of electrons results in the formation of single covalent bond. 

Sharing of two pairs of electrons results in the formation of double covalent bond.

 Sharing of three pairs of electrons results in the formation of triple covalent bond.

Formation of single covalent bond in Hydrogen  molecule 

The atomic number of hydrogen is 1, its electronic arrangement is 1, it has 1 valence electron. It needs 1 electron more to attain stability. So two hydrogen atoms share 1 pair of electrons resulting in the formation of a single covalent bond in hydrogen molecule H2.        

Few Examples 

of covalent bond formation 

4. Formation of a very large number of carbon compounds :-

 Carbon forms a very large number of compounds. The number of carbon compounds is more than three million. It is more than the number of compounds formed by all other elements. This is because 

 i) Carbon atom can form bonds with other carbon atoms to form long chains, branched chains  and closed rings. This property is called     catenation. 

ii) Since the valency of carbon is 4, it can form bonds with other     carbon atoms or with atoms of other elements like hydrogen,     oxygen, nitrogen, halogens etc.

Catenation 

The property of carbon combining with itself 

5. Hydrocarbons, Saturated and Unsaturated hydrocarbons :-

• Hydrocarbons :-  are compounds containing carbon and hydrogen      atoms.

• Saturated hydrocarbons :-  are hydrocarbons having all single      covalent bonds between the carbon atoms.      Eg : Alkanes .

• Unsaturated hydrocarbons :-  are hydrocarbons having a double or     triple covalent bond between two carbon atoms. Eg : Alkenes and     Alkynes.

Alkanes :-

examples

Alkenes

example

Alkynes 

Example

Multiple Choice

The saturated hydrocarbons having single bonds are called

• Alkenes

• Alkanes

• Alkynes

6. Isomerism 

Carbon compounds having the same molecular formula but different structural formulae are called isomers. This property is called isomerism.

 Eg:- Butane – C4H10 has 2 isomers. They are Normal butane and Iso butane.

Pentane – C5H12 has 3 isomers. They are Normal pentane, Iso pentane and Neo   pentane.     

7. Functional groups :-

An atom or a group of atoms which decides the properties of a carbon compound is called a functional group.

Functional groups 

Example 

Poll

Do functional groups decide the property of a compound

• Yes

• No

8. Homologus series :-

 Homologus series is a group of carbon compounds having similar structures, similar chemical properties and whose successive members differ by a – CH2 group. Eg :- Alkanes, Alkenes, Alkynes etc. 

Poll

homologous series of compounds differ by a CH2

unit.

• Yes

• No

Chemical properties of carbon compounds

Chemical properties of carbon compounds

Chemical properties of carbon compounds

Hydrogenation 

  The addition of hydrogen to unsaturated hydrocarbons to form saturated hydrocarbons is called hydrogenation.  Hydrogenation is used to convert unsaturated oils and fats to saturated oils and fats.

Some important carbon compounds 

Some important carbon compounds 

Soaps 

Soaps are long chain sodium or potassium salts of carboxylic acids.      Eg:- Sodium stearate – C17H35COONa      

 Structure of soap molecule :-  A soap molecule has two parts. A long hydrocarbon part which is hydrophobic (water repelling) and soluble in oil and grease and a short ionic part which is  hydrophyllic (water attracting) and insoluble in oil and grease.

detergents 

Detergents are long chain sodium salts of sulphonic acids.      

 Soaps do not wash well with hard water because it forms insoluble precipitates of calcium and magnesium salts in hard water.      

    Detergents wash well with hard water because it does not form insoluble precipitates of calcium and magnesium salts in hard water.

Cleansing action of soap 

 When soap is dissolved in water it forms spherical structures called micelles. In each micelle the soap molecules are arranged radially such that the hydrocarbon  part is towards the centre and the ionic part is towards the outside. The HC part dissolves the dirt, oil and grease and forms an emulsion at the centre of the micelles which can be washed away by water.