Solid state quivck revision

 

Chapter 1: Solid State – Ultra Quick Revision

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1.1 Introduction

• Strong interparticle forces of attraction.
• Fixed shape and fixed volume.
• Very small change with temperature and pressure.
• Particles may be atoms, ions or molecules.

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1.2 Types of Solids

Crystalline Solids

• Regular, repeating arrangement.
• Long-range order.
• Sharp melting point.
• Anisotropic (properties differ with direction).
• Examples: Ice, NaCl, Diamond, Graphite, Gold, Copper.

Amorphous Solids

• Random arrangement.
• Short-range order.
• No sharp melting point.
• Isotropic (same properties in every direction).
• Examples: Glass, Plastic, Rubber, Tar.

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Crystalline vs Amorphous

Crystalline	Amorphous
Regular arrangement	Random arrangement
Long-range order	Short-range order
Sharp melting point	No sharp melting point
Anisotropic	Isotropic

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1.2.3 Isomorphism, Polymorphism & Allotropy

Isomorphism

• Different substances → Same crystal structure.
• Same atomic ratio.
• Examples: NaF & MgO, NaNO₃ & CaCO₃.

Polymorphism

• One substance → Different crystal structures.
• Examples: Calcite & Aragonite, Quartz forms.

Allotropy

• Polymorphism shown by elements.
• Example: Diamond, Graphite, Fullerene.

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1.3 Classification of Crystalline Solids

Type	Particles	Force	Properties
Ionic	Ions	Electrostatic	Hard, brittle, high MP, conducts when molten or aqueous.
Covalent	Atoms	Covalent Bond	Very hard, high MP/BP, poor conductor.
Molecular	Molecules	Intermolecular	Soft, low MP, insulator.
Metallic	Metal Atoms	Metallic Bond	Malleable, ductile, good conductor.

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Examples

• Ionic: NaCl, KCl, CaF₂
• Covalent: Diamond, Quartz, Boron Nitride
• Molecular: Cl₂, CH₄, CO₂, O₂, H₂
• Metallic: Fe, Au, Ag, Na, K

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1.4 Crystal Structure

Lattice

• Regular 3D arrangement of points.

Basis

• Atom, ion or molecule attached to each lattice point.

Crystal = Lattice + Basis

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1.4.2 Unit Cell

• Smallest repeating unit of a crystal.
• Repeats to form the whole crystal.
• a, b, c → Edge lengths.
• α, β, γ → Angles.

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1.4.3 Types of Unit Cell

• Primitive: Particles only at corners.
• Body-Centred (BCC): Corners + one at centre.
• Face-Centred (FCC): Corners + one at each face.
• Base-Centred: Corners + centres of two opposite faces.

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🚀 One-Page Memory Sheet

• ✅ Strong force → Solid
• ✅ Fixed shape + Fixed volume
• ✅ Particles = Atoms / Ions / Molecules
• ✅ Crystalline = Regular + Long-range + Sharp MP + Anisotropic
• ✅ Amorphous = Random + Short-range + No Sharp MP + Isotropic
• ✅ Isomorphism = Different substances + Same crystal
• ✅ Polymorphism = Same substance + Different crystals
• ✅ Allotropy = Polymorphism in elements
• ✅ Ionic → Ions → Electrostatic
• ✅ Covalent → Atoms → Covalent Bond
• ✅ Molecular → Molecules → Intermolecular Force
• ✅ Metallic → Metal Atoms → Metallic Bond
• ✅ Crystal = Lattice + Basis
• ✅ Unit Cell = Smallest repeating unit
• ✅ Parameters = a, b, c, α, β, γ
• ✅ Unit Cells = Primitive, BCC, FCC, Base-Centred