Group 14 Elements - Carbon Family

Real-Life Connection: From Diamond Rings to Computer Chips

The same element that makes diamond engagement rings also creates the graphite in your pencil! Carbon’s versatility is unmatched - it forms life molecules (DNA, proteins) and industrial materials (carbon fiber, graphene). Silicon, carbon’s neighbor, revolutionized technology - the “Silicon Valley” isn’t named randomly! Silicones (not silicon) waterproof your shoes and seal your bathroom tiles.

Group 14 Elements Overview

Members: Carbon (C), Silicon (Si), Germanium (Ge), Tin (Sn), Lead (Pb)

Electronic Configuration Pattern

• General configuration: ns² np²
• Carbon: [He] 2s² 2p²
• Silicon: [Ne] 3s² 3p²
• Germanium: [Ar] 3d¹⁰ 4s² 4p²

Memory Trick - “Can’t See German Snakes Properly”: C, Si, Ge, Sn, Pb

Key Trends Down the Group

Memory Trick for Oxidation States: “Carbon Plus Four, Lead Plus Two” - C prefers +4, Pb prefers +2

Interactive Demo: Visualize Group 14 in Periodic Table

Explore the carbon family elements and their position in the periodic table.

Carbon - The Element of Life

Unique Properties of Carbon

1. Tetravalency: Forms 4 covalent bonds
2. Catenation: Forms long chains (millions of atoms!)
3. Multiple bonding: Can form C=C and C≡C bonds
4. Small size: Strong π-π overlap possible

Why is carbon unique?

• Small size allows effective π-bonding
• Similar electronegativity of C and H (stable C-H bonds)
• Strong C-C bonds (348 kJ/mol)

Allotropes of Carbon

Definition: Different structural forms of the same element in the same physical state

1. Diamond

Structure:

• 3D tetrahedral network
• Each C is sp³ hybridized
• C-C bond length: 154 pm
• Very hard (hardest natural material)

Properties:

• Non-conductor of electricity (no free electrons)
• High refractive index (brilliance)
• High thermal conductivity
• Density: 3.51 g/cm³

Uses: Jewelry, cutting tools, drill bits

Memory Trick: “Diamond = Dense & Drill” - 3D structure, very dense, used for drilling

2. Graphite

Structure:

• Layered structure (2D sheets)
• Each C is sp² hybridized
• Hexagonal rings in layers
• C-C bond in layer: 141.5 pm
• Layer separation: 335 pm
• Delocalized π-electrons above and below plane

Properties:

• Good conductor of electricity (delocalized electrons)
• Soft and slippery (weak van der Waals between layers)
• Black and opaque
• Density: 2.26 g/cm³

Uses: Lubricant, electrodes, pencil leads, moderator in nuclear reactors

Memory Trick: “Graphite = Glides & Guides” - Slippery (lubricant), conducts electricity (guides electrons)

3. Fullerenes (C₆₀, C₇₀, etc.)

Structure:

• Spherical or ellipsoidal
• C₆₀ (Buckminsterfullerene): Soccer ball shape
• 12 pentagons + 20 hexagons
• Each C is sp² hybridized

Discovery: 1985 by Kroto, Curl, and Smalley (Nobel Prize 1996)

Properties:

• Dark solid
• Soluble in benzene (purple solution)
• Poor conductor

Uses: Drug delivery, superconductors (when doped with K)

4. Graphene

Structure:

• Single layer of graphite
• One atom thick 2D sheet
• sp² hybridized carbon
• Strongest material known

Properties:

• Excellent conductor
• Transparent
• Extremely strong (200 times stronger than steel)
• High thermal conductivity

Uses: Electronics, sensors, composite materials

Memory Trick for Allotropes: “DGFG” - Diamond (3D, sp³), Graphite (2D layers, sp²), Fullerenes (0D, sp²), Graphene (2D sheet, sp²)

Comparison Table: Diamond vs Graphite

Important Carbon Compounds

Carbon Monoxide (CO)

Preparation:

1. Laboratory: HCOOH --conc. H₂SO₄--> CO + H₂O (180°C)
2. Industrial: C + ½O₂ → CO (limited oxygen)
              CH₄ + H₂O → CO + 3H₂ (water gas)

Properties:

• Neutral oxide (neither acidic nor basic)
• Toxic (binds to hemoglobin 300× more strongly than O₂)
• Good reducing agent
• Forms metal carbonyls: Ni + 4CO → Ni(CO)₄

Uses: Reducing agent in metallurgy, fuel

Carbon Dioxide (CO₂)

Preparation:

1. Lab: CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
2. Lab: NaHCO₃ + HCl → NaCl + H₂O + CO₂
3. Industrial: CaCO₃ --heat--> CaO + CO₂

Properties:

• Acidic oxide
• Linear molecule (sp hybridized C)
• Sublimes at -78°C (dry ice)

Reactions:

CO₂ + H₂O → H₂CO₃ (carbonic acid)
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O (milky - lime water test)
Excess CO₂ + CaCO₃ + H₂O → Ca(HCO₃)₂ (soluble - milkiness disappears)
CO₂ + 2Mg → 2MgO + C (burns in CO₂ - shows it's not for fire extinguishing Mg fires!)

Memory Trick: “CLECC” - CO₂, Limewater, Excess clears, Carbonates, Can’t extinguish Mg

Silicon - The Semiconductor

Occurrence

• Second most abundant element in Earth’s crust (27.7%)
• Always found combined (SiO₂, silicates)
• Common minerals: Quartz, sand, feldspar, mica

Preparation

Laboratory:

SiO₂ + 2Mg → 2MgO + Si (impure)

Ultrapure Silicon (for semiconductors):

Si(impure) + 2Cl₂ → SiCl₄
SiCl₄ + 2H₂ → Si(pure) + 4HCl (at 1000°C)
Further purified by zone refining

Silicon Dioxide (SiO₂)

Structure:

• 3D network of SiO₄ tetrahedra
• Each Si bonded to 4 O atoms
• Each O bonded to 2 Si atoms
• Very high melting point (1713°C)

Forms:

1. Crystalline: Quartz, cristobalite, tridymite
2. Amorphous: Silica gel, kieselguhr

Reactions:

SiO₂ + 2NaOH → Na₂SiO₃ + H₂O (sodium silicate)
SiO₂ + 4HF → SiF₄ + 2H₂O (only acid that attacks SiO₂)
SiO₂ + 2C → Si + 2CO (1800°C, electric furnace)
SiO₂ + CaO → CaSiO₃ (calcium silicate - in cement)

Memory Trick: “HNFC” - Only HF attacks silica, forms Na silicate with base, reacts with C

Silicones (Polysiloxanes)

General Formula: R₂SiO (where R = CH₃, C₂H₅, C₆H₅)

Structure:

• Backbone of alternating Si-O bonds
• Organic groups (R) attached to Si
• Linear, cyclic, or cross-linked polymers

Preparation:

Step 1: 2CH₃Cl + Si → (CH₃)₂SiCl₂ (Cu catalyst, 570K)
Step 2: (CH₃)₂SiCl₂ + 2H₂O → (CH₃)₂Si(OH)₂ + 2HCl
Step 3: n(CH₃)₂Si(OH)₂ → [-Si(CH₃)₂-O-]ₙ + nH₂O (polymerization)

Types and Uses:

1. Linear silicones (low cross-linking):

   • Silicone oils - lubricants
   • Hydraulic fluids

2. Cross-linked silicones:

   • Silicone rubber - gaskets, sealants
   • Water repellents

3. Highly cross-linked:

   • Silicone resins - paints, varnishes

Properties:

• Chemically inert
• Water repellent (hydrophobic)
• Heat resistant
• Good electrical insulator
• Biocompatible

Memory Trick: “SiOil = Silicone” - Si-O backbone with organic groups makes it oil-like and water-repellent

Silicates

Basic Unit: SiO₄⁴⁻ tetrahedron

Types (based on sharing of corners):

1. Orthosilicates (Island silicates):

   • SiO₄⁴⁻ (no sharing)
   • Example: Zircon (ZrSiO₄)

2. Pyrosilicates:

   • Si₂O₇⁶⁻ (one corner shared)
   • Example: Thortveitite (Sc₂Si₂O₇)

3. Cyclic silicates:

   • (SiO₃²⁻)ₙ (two corners shared, ring structure)
   • Example: Beryl (Be₃Al₂Si₆O₁₈)

4. Chain silicates:

   • (SiO₃²⁻)ₙ (two corners shared, linear chain)
   • Example: Pyroxenes

5. Sheet silicates:

   • (Si₂O₅²⁻)ₙ (three corners shared)
   • Example: Mica, Talc, Asbestos

6. 3D network:

   • (SiO₂)ₙ (all four corners shared)
   • Example: Quartz, Feldspar

Silicon Tetrachloride (SiCl₄)

Preparation:

Si + 2Cl₂ → SiCl₄ (at 570K)
SiO₂ + 2C + 2Cl₂ → SiCl₄ + 2CO

Hydrolysis (unlike CCl₄):

SiCl₄ + 2H₂O → SiO₂ + 4HCl

Why does SiCl₄ hydrolyze but CCl₄ doesn’t?

• Si has vacant d-orbitals (can expand octet)
• C cannot expand octet (no d-orbitals in 2nd shell)
• H₂O attacks Si forming intermediate with d-orbital involvement

Memory Trick: “Carbon Can’t Donate d-orbitals” - C has no d-orbitals, so CCl₄ doesn’t hydrolyze

Zeolites - Microporous Aluminosilicates

Structure:

• 3D framework of SiO₄ and AlO₄ tetrahedra
• Contain cavities and channels
• Exchangeable cations (Na⁺, Ca²⁺) in pores

Formula: Nₓ[(AlO₂)ₓ(SiO₂)y]·mH₂O

Uses:

• Water softeners (ion exchange)
• Molecular sieves (separation)
• Catalysts in petroleum refining
• Detergents

Comparison: Carbon vs Silicon

Memory Trick: “Carbon Creates Chains, Silicon Sees Dots” - C forms chains (catenation), Si has d-orbitals

Germanium, Tin, and Lead

Germanium (Ge)

• Metalloid
• Important semiconductor
• Used in transistors, infrared optics
• Ge-Ge bond weaker than Si-Si

Tin (Sn)

Allotropes:

• α-Sn (grey tin): Diamond structure, non-metallic
• β-Sn (white tin): Metallic, tetragonal structure

Conversion: β-Sn → α-Sn (below 13.2°C) - “tin pest” or “tin disease”

Compounds:

• SnCl₂ (stannous chloride): Reducing agent
• SnCl₄ (stannic chloride): Lewis acid

Uses: Solder, tin plating, bronze (Cu-Sn alloy)

Lead (Pb)

Oxidation States: +2 (stable) > +4 (less stable) - Inert pair effect

Important Compounds:

1. Lead oxides:

   • PbO (litharge): Yellow/red, amphoteric
   • Pb₃O₄ (red lead, minium): 2PbO·PbO₂
   • PbO₂: Strong oxidizing agent

2. Lead halides:

   • PbCl₂: Sparingly soluble in cold water, soluble in hot
   • PbI₂: Yellow precipitate (qualitative test)

Reactions:

Pb + 2HCl → PbCl₂ + H₂
PbO + 2HNO₃ → Pb(NO₃)₂ + H₂O
Pb(NO₃)₂ + 2KI → PbI₂ (yellow ppt) + 2KNO₃
PbO₂ + 4HCl → PbCl₂ + Cl₂ + 2H₂O

Uses: Lead-acid batteries, radiation shielding, pigments (now restricted due to toxicity)

Common Mistakes to Avoid

1. Mistake: CCl₄ and SiCl₄ both hydrolyze

   • Correct: Only SiCl₄ hydrolyzes (Si has d-orbitals)

2. Mistake: Diamond conducts electricity like graphite

   • Correct: Diamond is insulator (all electrons in σ bonds), graphite conducts (delocalized π electrons)

3. Mistake: CO₂ is neutral oxide

   • Correct: CO₂ is acidic oxide (forms H₂CO₃)

4. Mistake: Si shows +2 oxidation state commonly like Pb

   • Correct: Si prefers +4, Pb prefers +2 (inert pair effect in Pb)

5. Mistake: Silicones are same as silicon

   • Correct: Silicones are polymers with Si-O backbone (polysiloxanes)

6. Mistake: C-C bond is weaker than Si-Si bond

   • Correct: C-C (348 kJ/mol) > Si-Si (226 kJ/mol)

7. Mistake: All carbons in graphite are sp³ hybridized

   • Correct: sp² hybridized (explains conductivity)

Practice Problems

Level 1: JEE Main Basics

1. Arrange in order of decreasing catenation: C, Si, Ge, Sn

2. Why is diamond hard while graphite is soft? Explain based on structure.

3. Write equations for: a) Laboratory preparation of CO from formic acid b) Action of excess CO₂ on lime water

4. Why does SiCl₄ undergo hydrolysis but CCl₄ does not?

5. What is the hybridization of carbon in: a) Diamond b) Graphite c) Fullerene

Level 2: JEE Main Advanced

6. How would you prepare ultrapure silicon for semiconductor industry? Write equations.

7. Calculate the number of C-C bonds in C₆₀ (Buckminsterfullerene). Hint: Each C forms 3 bonds, total C atoms = 60

8. Explain why CO₂ is gas while SiO₂ is solid with very high melting point.

9. A white compound X on heating gives Y and water. Y turns lime water milky. When X is treated with dilute acid, effervescence occurs with evolution of Y. Identify X and Y.

10. Draw the structure of: a) Linear silicone b) Cyclic silicate (Si₃O₉⁶⁻)

Level 3: JEE Advanced

11. The C-C bond length in graphite is 141.5 pm while in diamond it is 154 pm. Explain this difference. Also explain why graphite has higher electrical conductivity than diamond.

12. An element X forms two oxides XO and XO₂. XO is neutral while XO₂ is acidic. XO₂ reacts with Mg even when burning. Identify X and write all reactions.

13. Silicones are water repellent. Explain this property based on structure. Why are they preferred over organic polymers in some applications?

14. Complete and balance: a) Si + NaOH + H₂O → b) Pb₃O₄ + HNO₃ → c) PbO₂ + HCl (conc.) →

15. A cyclic silicate anion has the formula (SiₙO₃ₙ)²ⁿ⁻. Each SiO₄ unit shares exactly two oxygen atoms with adjacent units. Derive n and draw the structure for n=3.

Cross-Links to Other Topics

Related to Periodic Classification

• Periodic Trends - Size and bond strength trends
• Inert Pair Effect - Pb(II) stability

Related to Chemical Bonding

• Hybridization - sp³ in diamond, sp² in graphite
• Pi Bonding - Graphite conductivity
• Three-Dimensional Structures - Diamond, SiO₂ networks

Related to Other Chapters

• Coordination Compounds - Metal carbonyls
• Polymers - Silicones as inorganic polymers
• Environmental Chemistry - CO₂ and greenhouse effect

Memory Palace for Group 14

Imagine a Silicon Valley Tech Campus:

Reception (Group overview):

• Sign: “Can’t See German Snakes Properly” (C, Si, Ge, Sn, Pb)
• Elevator display: ns² np² configuration

Diamond Cutting Room:

• 3D model of tetrahedral structure (sp³)
• Very hard cutting tools
• Non-conducting gloves required

Graphite Art Studio:

• Artists using pencils (graphite leads)
• Slippery floor (lubricant property)
• Electrical wires everywhere (conductor)
• 2D hexagonal artwork on walls

Fullerene Football Field:

• Giant C₆₀ soccer balls
• 12 pentagon + 20 hexagon markers
• Purple benches (C₆₀ in benzene is purple)

Silicon Factory:

• Pure Si crystals for computer chips
• HF tank (only acid that attacks SiO₂)
• Silicone sealant tubes everywhere
• Water droplets rolling off silicone-coated surfaces

Lead Battery Room:

• Lead-acid batteries
• Yellow PbI₂ paint on walls
• +2 oxidation state signs (inert pair effect)

Quick Revision Checklist

• Group 14 configuration: ns² np²
• Catenation order: C » Si > Ge > Sn > Pb
• Diamond: sp³, 3D, insulator, hardest
• Graphite: sp², 2D layers, conductor, soft
• Fullerenes: C₆₀ soccer ball structure
• CO is neutral, CO₂ is acidic oxide
• SiO₂ has 3D network, very high m.p.
• SiCl₄ hydrolyzes (d-orbitals), CCl₄ doesn’t
• Silicones: Si-O backbone, water repellent
• Inert pair effect: Pb(II) > Pb(IV)
• PbI₂ yellow precipitate test
• Tin pest: β-Sn → α-Sn below 13.2°C

Important Equations Summary

1. CO preparation: HCOOH --H₂SO₄--> CO + H₂O
2. Lime water: CO₂ + Ca(OH)₂ → CaCO₃ + H₂O
3. Excess CO₂: CaCO₃ + H₂O + CO₂ → Ca(HCO₃)₂
4. Pure Si: SiCl₄ + 2H₂ → Si + 4HCl
5. Silicate: SiO₂ + 2NaOH → Na₂SiO₃ + H₂O
6. HF attack: SiO₂ + 4HF → SiF₄ + 2H₂O
7. SiCl₄ hydrolysis: SiCl₄ + 2H₂O → SiO₂ + 4HCl
8. Silicone: 2CH₃Cl + Si --Cu--> (CH₃)₂SiCl₂
9. PbI₂ test: Pb(NO₃)₂ + 2KI → PbI₂ (yellow) + 2KNO₃
10. PbO₂ oxidation: PbO₂ + 4HCl → PbCl₂ + Cl₂ + 2H₂O

Last updated: July 2025 Previous: Group 13 Elements | Next: Group 15 Elements