Online Notes on Chapter=4 ( Carbon and Its compounds) Part 1

This is Online Notes on Chapter=4 ( Carbon and Its compounds) Part 1 for preparation of CBSE BOARD Examination, NTSE etc

Introduction :
• The element carbon is non-metal. Its symbol is C.

• Carbon is versatile element present in earth crust in form of mineral is
0.02% and atmosphere as CO2 is 0.03%.

• All the living things, plants and animals are made up of carbon based
compounds.


=> Carbon always form covalent bonds :

The atomic number of carbon is 6.
Electronic configuration :
            K   L
C (6)    2    4

=> How carbon attain noble gas configuration ?

(i) Carbon is tetravalent, it does not form ionic bond by either losing four
electrons (C4+) or by gaining four electrons (C4−). It is difficult to hold
four extra electron and would require large amount of energy to remove
four electrons. So, carbon can form bond by sharing of its electrons with
the electrons of other carbon atom or with other element and attain noble
gas configuration.

(ii) The atoms of other elements like hydrogen, oxygen and nitrogen,
chlorine also form bonds by sharing of electrons.

(iii) The bond formed by sharing of electrons between same or different
atoms is covalent bond.

(i)H2

(ii) O2

(iii) N2

Molecule of water has single covalent bond between one oxygen and two
hydrogen atoms.

=> Physical Properties of Covalent Compounds:

(a) Covalent compounds have low melting and boiling points as they have
weak intermolecular force.

(b) They are generally poor conductor of electricity as electrons are shared
between atoms and no charged particles are formed.


=> Versatile Nature of Carbon:
The two characteristic properties of carbon element which lead to the formation
of large number of compounds :

(i) Catenation : Carbon can link with carbon atoms by means of covalent
bonds to form long chains, branched chains and closed ring. Compound
Carbon atoms may be linked by single, double or triple bonds.

(ii) Tetravalency : Carbon has 4 valence electrons. Carbon can bond with
four carbon atoms, monovalent atoms, oxygen, nitrogen and sulphur.


=> Saturated and Unsaturated Carbon Compounds:
Compounds made up of hydrogen and carbon are called hydrocarbon.

• Single bond between carbon                   • Double or triple bond between
atoms. carbon atoms.
• – C – C –                                                 • – C = C – – C ≡ C –
• Alkanes                                                    • Alkenes             Alkynes
General formulae
CnH2n + 2                                                    CnH2n              CnH2n – 2

=> Electron Dot Structure of Saturated Hydrocarbons:
Ethane C2H6

The names, molecular formulae and saturated formulae of saturated
hydrocarbons (alkanes) are given below:

=> Electron Dot Structure of Unsaturated Hydrocarbons:

=> Carbon Compounds on the Basis of Structure:
(i) Straight (unbranched) chain

(ii) Branched

These three above compounds has same molecular formula but different
structures are called structural isomers and phenomenon is structural isomerism.
(iii) Cyclic

=> Functional Groups:
• In hydrocarbon chain, one or more hydrogen atom is replaced by other
atoms in accordance with their valancies. These are heteroatom.
• These heteroatom or group of atoms which make carbon compound
reactive and decides its properties are called functional groups