Chemical Bonding IGCSE Chemistry: Complete Mastery Guide with Memory Tips

🔗 Understanding Chemical Bonding in IGCSE Chemistry

Chemical bonding explains how atoms combine to form compounds. This comprehensive IGCSE Chemistry guide covers ionic, covalent, and metallic bonding with proven memory techniques and practical applications.

📚 Key Theory: Types of Chemical Bonds

1. Ionic Bonding

Definition: Electrostatic attraction between oppositely charged ions Formation: Transfer of electrons from metal to non-metal Examples: NaCl, MgO, CaCl₂

2. Covalent Bonding

Definition: Sharing of electron pairs between atoms Formation: Non-metal atoms share electrons Examples: H₂O, CO₂, CH₄

3. Metallic Bonding

Definition: Attraction between metal cations and delocalized electrons Formation: Metal atoms lose electrons to form “electron sea” Examples: Cu, Fe, Al

🧠 Memory Tips and Techniques

1. Bonding Types Memory: “ICM”

• Ionic: Metal + Non-metal (electron transfer)
• Covalent: Non-metal + Non-metal (electron sharing)
• Metallic: Metal + Metal (electron sea)

2. Ionic vs Covalent: “Give vs Share”

• Ionic: GIVE electrons (transfer)
• Covalent: SHARE electrons (sharing)

3. Bond Strength Memory: “Triple > Double > Single”

• Triple bond: Strongest, shortest (C≡C)
• Double bond: Medium strength (C=C)
• Single bond: Weakest, longest (C-C)

4. Electronegativity Memory: “F-O-N-Cl”

Most electronegative elements: Fluorine > Oxygen > Nitrogen > Chlorine

📖 Ionic Bonding Detailed

Formation Process

1. Metal atoms lose electrons → positive cations
2. Non-metal atoms gain electrons → negative anions
3. Electrostatic attraction between opposite charges
4. Ionic lattice structure forms

Properties of Ionic Compounds

• High melting/boiling points: Strong electrostatic forces
• Conduct electricity: When molten or dissolved (mobile ions)
• Soluble in water: Polar water molecules surround ions
• Brittle: Layers shift, like charges repel
• Form crystals: Regular lattice arrangement

Common Ionic Compounds

• Sodium chloride (NaCl): Na⁺ + Cl⁻
• Magnesium oxide (MgO): Mg²⁺ + O²⁻
• Calcium fluoride (CaF₂): Ca²⁺ + 2F⁻

🔬 Covalent Bonding Detailed

Formation Process

1. Non-metal atoms approach each other
2. Electron orbitals overlap
3. Electron pair shared between nuclei
4. Covalent bond forms

Types of Covalent Bonds

• Single bond: One shared pair (H-H)
• Double bond: Two shared pairs (O=O)
• Triple bond: Three shared pairs (N≡N)

Properties of Covalent Compounds

• Low melting/boiling points: Weak intermolecular forces
• Don’t conduct electricity: No mobile charges
• Insoluble in water: Non-polar molecules
• Soft/flexible: Weak forces between molecules

Dot-and-Cross Diagrams

Water (H₂O):

• Oxygen: 6 outer electrons
• Each hydrogen: 1 electron
• Two covalent bonds formed

Methane (CH₄):

• Carbon: 4 outer electrons
• Each hydrogen: 1 electron
• Four covalent bonds formed

⚡ Metallic Bonding Detailed

Electron Sea Model

• Metal cations: Fixed in lattice positions
• Delocalized electrons: Mobile “electron sea”
• Electrostatic attraction: Between cations and electron sea

Properties of Metals

• Good electrical conductors: Mobile electrons
• Good thermal conductors: Electron movement transfers heat
• Malleable: Layers can slide over each other
• Ductile: Can be drawn into wires
• Metallic luster: Electrons reflect light

🎯 IGCSE Exam Focus Areas

Common Exam Questions

1. Draw dot-and-cross diagrams (4 marks)
2. Explain bonding in compounds (6 marks)
3. Predict properties from bonding (5 marks)
4. Compare different bond types (4 marks)

Exam Strategy

1. Identify elements involved
2. Determine bond type from element types
3. Draw appropriate diagrams
4. Explain properties based on bonding

📊 Electronegativity and Polarity

Electronegativity

Definition: Ability of an atom to attract bonding electrons Scale: Pauling scale (0.7 to 4.0) Trend: Increases across period, decreases down group

Bond Polarity

• Non-polar covalent: Equal sharing (same elements)
• Polar covalent: Unequal sharing (different electronegativity)
• Ionic: Complete transfer (large electronegativity difference)

Electronegativity Differences

• 0.0-0.4: Non-polar covalent
• 0.4-1.7: Polar covalent
• >1.7: Ionic

🧪 Intermolecular Forces

Van der Waals Forces

• London dispersion: Temporary dipoles (all molecules)
• Dipole-dipole: Permanent dipoles (polar molecules)
• Hydrogen bonding: H bonded to N, O, or F

Strength Order

Hydrogen bonding > Dipole-dipole > London dispersion

Effect on Properties

• Stronger forces: Higher boiling points
• Weaker forces: Lower boiling points
• Molecular size: Larger molecules, stronger London forces

🔄 Giant vs Simple Structures

Giant Ionic Structures

• Examples: NaCl, MgO, CaF₂
• Properties: High melting points, conduct when molten
• Structure: 3D lattice of ions

Giant Covalent Structures

• Examples: Diamond, graphite, silicon dioxide
• Properties: Very high melting points, usually don’t conduct
• Structure: 3D network of covalent bonds

Simple Molecular Structures

• Examples: H₂O, CO₂, CH₄
• Properties: Low melting points, don’t conduct
• Structure: Discrete molecules held by weak forces

💎 Allotropes of Carbon

Diamond

• Structure: Tetrahedral, 4 bonds per carbon
• Properties: Very hard, electrical insulator
• Uses: Cutting tools, jewelry

Graphite

• Structure: Layers, 3 bonds per carbon, delocalized electrons
• Properties: Soft, electrical conductor
• Uses: Pencils, electrodes, lubricants

Graphene

• Structure: Single layer of graphite
• Properties: Strongest material, excellent conductor
• Uses: Electronics, composites

🧬 Shapes of Molecules

VSEPR Theory

Principle: Electron pairs repel, adopt positions of minimum repulsion

Common Molecular Shapes

• Linear: 2 bonding pairs (BeCl₂)
• Trigonal planar: 3 bonding pairs (BF₃)
• Tetrahedral: 4 bonding pairs (CH₄)
• Pyramidal: 3 bonding + 1 lone pair (NH₃)
• Bent: 2 bonding + 2 lone pairs (H₂O)

🔬 Practical Applications

Ionic Compounds in Daily Life

• Table salt (NaCl): Food seasoning
• Calcium carbonate (CaCO₃): Antacids, chalk
• Sodium hydrogen carbonate (NaHCO₃): Baking soda

Covalent Compounds in Daily Life

• Water (H₂O): Essential for life
• Carbon dioxide (CO₂): Photosynthesis, carbonated drinks
• Methane (CH₄): Natural gas fuel

Metals in Daily Life

• Copper: Electrical wiring
• Iron: Construction, tools
• Aluminum: Packaging, aircraft

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