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Carbon and its Compounds | Class 10 CBSE | Web Notes | Part 2 - Versatile Nature of Carbon

VERSATILE NATURE OF CARBON

Carbon has two unique properties called Catenation & Tetravalency, enabling it to form millions of compounds, outnumbering compounds formed by all other elements combined.

1. Catenation

  • It is the ability of carbon to form bonds with other carbon atoms, creating large molecules.
  • They may be long chains, branched chains or ring forms.
  • No other element exhibits catenation like carbon. Silicon forms compounds with hydrogen which have chains of up to 7 or 8 atoms, but these are very reactive. Carbon-carbon bond is very strong & stable. This gives large number of compounds.

2. Tetravalency

  • Carbon can bond with four other atoms of carbon or some other monovalent elements.
  • Carbon compounds are formed with oxygen, hydrogen, nitrogen, sulphur, chlorine etc. giving specific properties.
  • Carbon atom is small sized. So the nucleus can hold the shared pairs of electrons strongly. So carbon can make very stable compounds with other elements. The bonds formed by elements having bigger atoms are weaker.
  • It was thought that organic or carbon compounds could only be formed with the help of a vital force (i.e., a living system is needed).
  • Friedrich Wöhler (1828) disproved this by preparing urea from ammonium cyanate.
  • But carbon compounds, except for carbides, oxides of carbon, carbonate and hydrogencarbonate salts are studied under organic chemistry.

Saturated and Unsaturated Carbon Compounds

Saturated Compounds

Contain only single bonds between carbon atoms; less reactive.

  • Example: Ethane (C2H6)

    • Structure:
    Ethane Structure

  • Example: Propane (C3H8)

    • Structure:
    Propane Structure


Unsaturated Compounds

Contain double or triple bonds between carbon atoms; more reactive.

  • Example: Ethene (C2H4)

    • It needs double bond to satisfy the valency.

    Ethene Structure

  • Ethyne (C2H2)

    • It has triple bond between carbon atoms to satisfy the valency (H – C ≡ C – H).

    Electron Dot Structure:
    Ethyne Electron Dot Structure

Chains, Branches, and Rings

Chains

Contain multiple carbon atoms.

No. of C atoms Name Formula Structure
1 Methane CH4 [Structure Image]
2 Ethane C2H6 [Structure Image]
3 Propane C3H8 [Structure Image]
4 Butane C4H10 [Structure Image]
5 Pentane C5H12 [Structure Image]
6 Hexane C6H14 [Structure Image]

Isomers

Compounds with the same molecular formula but different structures (e.g., C4H10 has two forms: n-butane and isobutane).

  • Structures:
    C4H10 Isomers

Rings

Carbon atoms arranged in a ring.

  • Example: Cyclohexane (C6H12)
  • Structure:
    Cyclohexane Structure
  • Example: Benzene (C6H6) (unsaturated cyclic compound)
  • Structure:
    Benzene Structure

Hydrocarbons

Compounds containing only carbon and hydrogen.

  • Alkanes: Saturated hydrocarbons (single bonds, CnH2n+2).
  • Alkenes: Unsaturated hydrocarbons with one or more double bonds (CnH2n).
  • Alkynes: Unsaturated hydrocarbons with one or more triple bonds (CnH2n-2).

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Carbon bonds with elements like halogens, oxygen, nitrogen, and sulphur.

  • Heteroatoms: Elements replacing hydrogen in a hydrocarbon chain.
  • Functional Groups: Heteroatoms or groups that impart specific properties to the compound, attached to the carbon chain via free valency.
  • Some functional groups in carbon compounds:
    Functional Groups Table

Homologous Series

It is a series of compounds with the same functional group, differing by a –CH2– unit.

Examples

  • Alkanes: CH4, C2H6, C3H8, C4H10 (differ by –CH2–, 14 u mass difference).

    • General formula: CnH2n+2

  • Alkenes: C2H4, C3H6, C4H8 (differ by –CH2–).

    • General formula: CnH2n

  • Alkynes: C2H2, C3H4, C4H6 (differ by –CH2–).

    • General formula: CnH2n-2

  • Alcohols: CH3OH, C2H5OH, C3H7OH, C4H9OH (differ by –CH2–, 14 u mass difference).
Compounds Difference in Formula Difference in Molecular Mass
CH3OH & C2H5OH –CH2– 14 U
C2H5OH & C3H7OH –CH2– 14 U
C3H7OH & C4H9OH –CH2– 14 U
C4H9OH & C5H11OH –CH2– 14 U

As the molecular mass increases, physical properties such as melting & boiling points, solubility in solvent etc. also increase. But chemical properties remain similar.

Nomenclature of Carbon Compounds

Method:

  1. Identify the number of carbon atoms (e.g., three carbons = propane).
  2. Indicate the functional group with a prefix or suffix.
  3. If the suffix starts with a vowel, remove the final ‘e’ from the carbon chain name (e.g., propane + ketone = propan + one = propanone).
  4. For unsaturated compounds, replace ‘ane’ with ‘ene’ (double bond) or ‘yne’ (triple bond) (e.g., propene, propyne).

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1. Bonding in Carbon - the Covalent Bond 2. Versatile Nature of Carbon 3. Chemical properties of Carbon Compounds 4. Some important Carbon Compounds 5. Soaps and Detergents
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