Structures and Properties

🏗️ Chemical Bonding: Structures and Properties

The LEGO City Analogy

Imagine you’re building with LEGO blocks. Some structures use just a few blocks snapped together — easy to take apart. Others use millions of blocks locked together in every direction — super strong and almost impossible to break!

Atoms work the same way. How they connect decides if something melts easily, conducts electricity, or is hard as a diamond!

🏠 Molecular vs Giant Structures

Two Ways to Build

Think of two LEGO creations:

1. A small car (5-10 blocks) — Easy to pick up, move, break apart
2. A massive castle (millions of blocks all connected) — Heavy, strong, won’t budge!

Example:

• Water (H₂O) = Molecular. Each water molecule is separate. Boils at 100°C.
• Diamond = Giant. Every carbon atom connected to every neighbor. Melts at 3,550°C!

💎 Diamond Structure

The Ultimate LEGO Castle

Imagine building a structure where:

• Every block connects to exactly 4 neighbors
• Every connection is equally strong
• The pattern goes on forever in all directions

That’s diamond!

graph TD
    C1["Carbon"] --- C2["Carbon"]
    C1 --- C3["Carbon"]
    C1 --- C4["Carbon"]
    C1 --- C5["Carbon"]
    C2 --- C6["..."]
    C3 --- C7["..."]
    C4 --- C8["..."]
    C5 --- C9["..."]

Why Diamond is Special

Real Life: Diamond drill bits cut through concrete!

✏️ Graphite Structure

The Sticky Note Stack

Now imagine a different build:

• Each carbon connects to only 3 neighbors (not 4)
• This makes flat sheets (like paper)
• Sheets stack on top with weak forces between them

graph TD
    subgraph Layer1["Sheet 1"]
        A1["C"] --- A2["C"]
        A2 --- A3["C"]
        A3 --- A1
    end
    subgraph Layer2["Sheet 2"]
        B1["C"] --- B2["C"]
        B2 --- B3["C"]
        B3 --- B1
    end
    Layer1 -.-> |Weak forces| Layer2

Graphite’s Superpowers

Real Life:

• Pencil “lead” = graphite! Layers rub off onto paper.
• Used in batteries and lubricants!

🏔️ Silicon Dioxide Structure

The Sand Castle That Never Breaks

Silicon dioxide (SiO₂) is like diamond’s cousin:

• Each silicon connects to 4 oxygens
• Each oxygen connects to 2 silicons
• Goes on forever — a giant covalent network

graph TD
    Si1["Silicon"] --- O1["Oxygen"]
    Si1 --- O2["Oxygen"]
    Si1 --- O3["Oxygen"]
    Si1 --- O4["Oxygen"]
    O1 --- Si2["Silicon"]
    O2 --- Si3["Silicon"]

Silicon Dioxide Properties

Real Life:

• Sand on the beach = silicon dioxide!
• Glass windows = melted and cooled SiO₂
• Quartz crystals in watches!

⚖️ Comparing Giant Structures

The Big Three Showdown

The Pattern

No free electrons = No conductivity

Only graphite has electrons that aren’t busy bonding!

⚡ Ionic vs Covalent Compounds

Sharing vs Giving Away

Covalent (Sharing LEGO):

• Atoms SHARE electrons
• Like two kids holding the same toy together
• Forms molecules (H₂O) or giant structures (diamond)

Ionic (Giving Away LEGO):

• One atom GIVES electrons to another
• Creates charged particles (ions)
• Opposites attract → form crystal lattice

graph LR
    subgraph Covalent
        A["Atom"] ---|Shared electrons| B["Atom"]
    end
    subgraph Ionic
        C["Metal +"] -->|Gave electron| D["Non-metal −"]
    end

Quick Comparison

🌡️ Structure and Melting Point

Why Some Things Melt Easily

The Rule: To melt something, you must break the forces holding it together.

Examples That Make Sense

Remember:

• Molecular = low melting point (weak forces)
• Giant = high melting point (strong bonds)

💡 Structure and Conductivity

Can Electricity Flow?

The Rule: Electricity needs MOVING CHARGED PARTICLES (electrons or ions).

The Conductivity Checklist

Why Graphite is Special

In graphite:

• Each carbon uses 3 electrons for bonding
• 1 electron is FREE to move
• These free electrons = electricity can flow!

graph TD
    subgraph Diamond
        D1["All 4 electrons busy"] --> D2["No free electrons"]
        D2 --> D3["Cannot conduct"]
    end
    subgraph Graphite
        G1["3 electrons busy"] --> G2["1 electron FREE"]
        G2 --> G3["CAN conduct!"]
    end

Ionic Conductivity Explained

Solid salt: Ions are LOCKED in place. Can’t move = No conduction.

Molten salt (liquid): Ions are FREE to move around. Moving charges = Conducts electricity!

Salt dissolved in water: Same idea — ions can move freely!

🎯 The Big Picture

graph TD
    A["How are atoms arranged?"] --> B{Giant or Molecular?}
    B --> |Molecular| C["Low melting point"]
    B --> |Giant| D["High melting point"]

    D --> E{Any free electrons?}
    E --> |Yes - Graphite| F["Conducts electricity"]
    E --> |No - Diamond, SiO2| G["Does NOT conduct"]

    C --> H{Any free electrons?}
    H --> |No| I["Does NOT conduct"]

Summary Table

🏆 You Made It!

Now you understand:

• ✅ Why diamond is super hard but doesn’t conduct
• ✅ Why graphite is soft AND conducts electricity
• ✅ Why salt only conducts when melted
• ✅ How to predict properties from structure!

The secret? It’s all about how atoms connect and whether anything is free to move!