Group 14 Elements Revision Notes, Mnemonics and Trends

Group 14 Elements (Carbon Family): C, Si, Ge, Sn, Pb, Fl

This quick revision Notes, Trends and Mnemonics are very important for CSIR-NET, GATE, SLET, NEET, JEE Main/Advanced, IIT-JAM.

Mnemonics: C: कहे | Si: सीता |Ge: जी | Sn: सुनो | Pb: प्रभु

1. General Electronic Configuration

ns² np² (four valence electrons → maximum oxidation state +4; +2 increases down group)

2. Key Periodic Trends (Down the Group: C → Pb)

Property	Trend	Exception/Important Note
Atomic & Ionic Radius	Increases	C < Si < Ge < Sn < Pb Exception: Slight anomaly Ge-Sn due to d-block contraction
Ionisation Energy	Decreases	C > Si > Ge > Sn > Pb +4 state stability: C > Si > Ge > Sn > Pb (inert pair effect)
Electronegativity	Decreases	C (2.5) > Si (1.8) > Ge (2.0) > Sn ≈ Pb
Metallic Character	Increases	C (non-metal) → Si, Ge (metalloids) → Sn, Pb (metals)
Melting & Boiling Point	Decreases (generally)	C (very high, diamond) > Si > Ge > Sn > Pb Pb low MP
Catenation	Decreases sharply	C >> Si > Ge > Sn > Pb Carbon maximum catenation
Allotropy	—	C (diamond, graphite, fullerene), Sn (grey/white), Pb (no)
Oxidation States	+2, +4	+4 dominant for C, Si, Ge; +2 dominant for Pb (inert pair effect)

3. Anomalous Behaviour of Carbon

• Small size, high electronegativity, absence of d-orbitals, strong pπ-pπ multiple bonds
• Maximum catenation, forms stable multiple bonds (C=C, C≡C, C=O)
• Only +4 state stable, no +2
• Acidic oxides (CO₂)
• Forms organometallics easily

4. Important Compounds & Reactions

• Carbon Compounds:
  • CO (neutral), CO₂ (acidic), reducing agent
  • Carbides: Ionic (CaC₂ → acetylene), covalent (SiC → carborundum)
  • Fullerenes, graphene, CNTs
• Silicon Compounds:
  • SiO₂ (acidic, quartz, sand)
  • Silicates (network structure, pyroxenes, amphiboles)
  • Silicones (polymer, water repellent)
  • Silanes (SiₙH₂ₙ₊₂, up to n=8)
• Tin & Lead:
  • SnCl₂ (reducing agent), PbCl₂ (less soluble)
  • SnO amphoteric, PbO basic (litharge, massicot)
• Hydrides: CH₄ (most stable) > SiH₄ > GeH₄ > SnH₄ > PbH₄ (least stable)
• Halides:
  • CX₄ (tetrahedral, stable)
  • SiX₄ (reactive with water)
  • SnX₄, PbX₄ (PbF₄ stable, PbI₄ does not exist)
  • SnX₂, PbX₂ more stable for heavier halogens
• Oxides: CO₂, SiO₂ acidic → GeO₂ amphoteric → SnO₂, PbO₂ amphoteric → PbO basic

5. Exam Tricks & Mnemonics

Inert Pair Effect: +2 stability: C < Si < Ge < Sn < Pb
Pb²⁺ much more stable than Pb⁴⁺.

Catenation Order: C >> Si > Ge ≈ Sn > Pb
Carbon forms longest chains → organic chemistry.

Thermal Stability of Hydrides: CH₄ > SiH₄ > GeH₄ > SnH₄ > PbH₄
Decreases down group.

Acidic Nature of Dioxides: CO₂ > SiO₂ > GeO₂ > SnO₂ > PbO₂
Decreases → PbO basic.

Reducing Power of +2 Oxides: CO > SnO > PbO (CO strongest reducing).

Stability of Tetrahalides: CX₄ > SiX₄ > GeX₄ > SnX₄ > PbX₄
PbI₄ does not exist (Pb⁴⁺ oxidises I⁻).

6. Frequently Asked Exam Questions

• Why carbon shows maximum catenation?
• Inert pair effect in group 14?
• Why Pb²⁺ more stable than Pb⁴⁺?
• Structure of SiO₂ vs CO₂?
• Why Si does not form multiple bonds like carbon?
• Amphoteric nature of SnO₂/PbO₂?
• Why diamond is hard but graphite soft?
• Silicones properties & uses?

7. Quick Revision One-Liners

• Carbon: non-metal, allotropes, organic backbone.
• Silicon: 2nd most abundant, semiconductors, silicates.
• Germanium: metalloid, used in transistors.
• Tin: white (β) & grey (α) allotropes, tin plague.
• Lead: toxic, +2 dominant, used in batteries (PbO₂ cathode).
• CO neutral oxide, CO₂ acidic anhydride of H₂CO₃.
• SiO₂ does not react with water, but with HF → SiF₄.