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ChemistryMediumClass 11

Group 14 — Carbon family, allotropes of carbon

p-block Elements (Class 11 — Groups 13 & 14)

10

JEE Qs

8%

Hard

75

min

Focus on the unique properties of carbon, the structural differences of its allotropes and how these dictate their physical and chemical properties, and the inert pair effect's impact on oxidation state stability for heavier elements.

✅ Key Points for JEE

  • 1Anomalous behavior of Carbon: Due to its small size, high electronegativity, high ionization enthalpy, and absence of d-orbitals, carbon exhibits unique properties like catenation and ability to form pπ-pπ multiple bonds.
  • 2General trends down Group 14: Atomic size, metallic character, and stability of +2 oxidation state increase (due to inert pair effect for Sn and Pb). Electronegativity, ionization enthalpy, and stability of +4 oxidation state decrease.
  • 3Allotropes of Carbon: Understand the distinct structures (diamond: sp³ 3D network; graphite: sp² layered 2D sheets; fullerenes: sp² cage-like structures; graphene: sp² single 2D sheet), hybridization, bonding, and resulting physical properties (hardness, conductivity, thermal stability).
  • 4Difference between Diamond and Graphite: Diamond is a hard insulator with sp³ hybridization and covalent bonds throughout; graphite is a soft conductor with sp² hybridization, delocalized electrons, and weak van der Waals forces between layers.
  • 5Oxidation States Stability: Carbon, Silicon, and Germanium primarily show +4 oxidation state. For Tin and Lead, the +2 oxidation state becomes increasingly stable due to the inert pair effect (Pb²+ is more stable than Pb⁴⁺ in many compounds).

⚠️ Common Mistakes

  • ✕Confusing the hybridization and resulting properties (e.g., electrical conductivity, hardness) of diamond (sp³, insulator, hard) and graphite (sp², conductor, soft).
  • ✕Incorrectly identifying the most stable oxidation state for Tin and Lead; remember +2 stability increases down the group, making Pb²⁺ more stable than Pb⁴⁺.
  • ✕Overlooking the implications of carbon's absence of d-orbitals, which prevents it from expanding its octet or forming compounds like [CCl₆]²⁻, unlike silicon.

NCERT Chapters

  • Class 11 Chemistry Ch 11: The p-Block Elements