CARBON AND ITS COMPOUNDS (CBSE 10TH NCERT CHAPTER 4 IMPORTANT KEY NOTES)

1. Covalent Bonding in Carbon

• Carbon has 4 valence electrons → Needs 4 more to complete octet.

• Forms covalent bonds by sharing electrons.

• Covalent bond: Formed by sharing of electrons between atoms.

• Common covalent compounds: Methane (CH₄), Ethane (C₂H₆), Water (H₂O), Ammonia (NH₃).

COVALENT BOND

2. Allotropes of Carbon

• Allotropes: Different forms of the same element.

• Diamond: Hardest, bad conductor of electricity.

• Graphite: Soft, good conductor of electricity.

• Fullerenes (C₆₀): Spherical molecules.

DIAMOND

GRAPHITE

FULLERENE

3. Versatile Nature of Carbon

• Catenation: Carbon can form long chains with itself.

• Tetravalency: Forms 4 covalent bonds → Variety of stable compounds.

• 

  FORMATION OF CHAINS

  Forms chains (straight, branched, rings) with single, double or triple bonds.

CATENATION

  

TETRAVALENT CARBON

4. Saturated and Unsaturated Compounds

• Saturated hydrocarbons (Alkanes): Single bonds only → CnH₂n+₂

• Unsaturated hydrocarbons:

  Alkenes: At least one double bond → CnH₂n
• Alkynes: At least one triple bond → CnH₂n−₂

5. Functional Groups

• Group of atoms that define chemical properties.
  
  |-------------------------
  | Alcohol | –OH | Ethanol | functional group(-OH)
  | Aldehyde | –CHO | Ethanal |functional group(-CHO)
  | Ketone | –CO– | Propanone |functional group(-CO-)
  | Carboxylic Acid | –COOH | Ethanoic acid |functional group(-COOH)
  | Halogen | –Cl, –Br, –I | Chloromethane |functional group(-Cl, -Br, -I)

6. Nomenclature of Organic Compounds

1. Identify longest carbon chain (root word).

2. Number the chain.

3. Name substituents/functional group.

4. Combine: position – substituent – parent chain – functional group.

Example: CH₃–CH₂–OH → Ethanol

7. Chemical Properties of Carbon Compounds 

Combustion

• Hydrocarbons + O₂ → CO₂ + H₂O + heat

CH₄ + 2O₂ → CO₂ + 2H₂O

➤ Oxidation

• Alcohols can be oxidized to acids.

CH₃CH₂OH + [O] → CH₃COOH

➤ Addition Reaction (Unsaturated)

• Unsaturated compounds + H₂ (in presence of catalyst like Ni/Pt).

CH₂=CH₂ + H₂ → CH₃–CH₃

➤ Substitution Reaction (Saturated)

• One hydrogen is replaced by another atom/group.

CH₄ + Cl₂ → CH₃Cl + HCl (in presence of sunlight)

8. Important Compounds

Ethanol (C₂H₅OH)

• Liquid, soluble in water, good solvent.

• Uses: Alcoholic drinks, antiseptic (hand sanitizer).

• Reactions:

  • Combustion: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

  • With acidified KMnO₄ → Acetic acid (oxidation)

Ethanoic Acid (CH₃COOH)

• Weak acid, vinegar contains 5–8%.

• Reactions:

  • With NaHCO₃: CH₃COOH + NaHCO₃ → CH₃COONa + CO₂ + H₂O

  • With alcohol (esterification): CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O

• 9. Soaps and Detergents 

• Soaps: Sodium/potassium salts of fatty acids.

• Micelles: Soap molecules form spherical structures in water that trap grease.

• Detergents: Synthetic, work in hard water, stronger cleaning

Important Diagrams to Practice

• Structure of methane, ethane, ethanol.

• Micelle formation.

• Electron dot structure of CH₄, O₂, N₂, H₂O.

Tips for Exam

• Understand structures and dot diagrams.

• Practice naming (nomenclature) thoroughly.

• Learn functional group identification.

• Revise chemical equations – especially combustion, oxidation, substitution.

• Solve numericals on molecular formulas and balancing equations.