💥 Bonding and Structure
Atoms bond to achieve a full outer electron shell, becoming more stable.
There are three main types of bonding:
⚡ Ionic (metal + non-metal)
🧬 Covalent (non-metal + non-metal)
🔩 Metallic (metal + metal)
The type of bonding affects a substance’s structure, melting point, electrical conductivity, and physical properties.
⚙️ Metallic Bonding
🔩 Found in pure metals and alloys (mixtures of metals).
🧲 How it works:
- Metal atoms lose their outer electrons to form positive ions.
- The lost electrons become delocalised — free to move throughout the structure.
- The electrostatic attraction between positive ions and negative delocalised electrons forms strong metallic bonds.
💡 Key features:
- Delocalised electrons → allow electricity and heat to flow easily.
- Layers of atoms can slide → metals are malleable and ductile.
- Strong bonds → high melting and boiling points.
⚗️ Alloys:
Adding other elements distorts layers → stops them sliding → makes metal harder.
🧱 Examples:
- Copper (Cu) – conducts electricity, used in wires.
- Iron (Fe) – strong, used in construction.
- Steel – alloy of iron + carbon, harder and less likely to rust.
🧬 Covalent Bonding
💞 When non-metal atoms share electrons to get full outer shells.
Each shared pair of electrons = one covalent bond.
📦 Properties:
- Strong bonds inside molecules, but weak forces between molecules.
- Low melting and boiling points (many are gases or liquids).
- Do not conduct electricity (no charged particles).
🧪 Examples:
- Water (H₂O) → Each H shares 1 electron with O.
- Oxygen (O₂) → Double bond (two shared pairs).
- Carbon dioxide (CO₂) → Two double bonds.
💎 Giant Covalent Structures
Some covalent substances form huge 3D lattices rather than small molecules.
Each atom is bonded to several others by strong covalent bonds.
🧱 Examples:
Diamond 💎
- Each carbon atom forms 4 strong covalent bonds.
- Very hard (each atom locked in place).
- Very high melting point.
- Does not conduct electricity (no free electrons).
Graphite ✏️
- Each carbon atom bonds to 3 others, forming layers of hexagons.
- Layers held together by weak forces → they can slide (soft and slippery).
- One electron per atom is delocalised → conducts electricity.
🧫 Graphene and Fullerenes
Graphene:
- A single layer of graphite (one atom thick).
- Strong, light, flexible.
- Excellent conductor of electricity and heat.
- Used in electronics, composites, and future nanotechnology.
Fullerenes:
- Molecules of carbon shaped like hollow tubes or spheres.
- Example: Buckminsterfullerene (C₆₀) – 60 carbon atoms in a football shape.
- Used in drug delivery, lubricants, and nanotubes for building strong materials.
⚡ Ionic Bonding
💥 Happens between metals and non-metals.
- Metal atoms lose electrons → form positive ions (cations).
- Non-metal atoms gain electrons → form negative ions (anions).
- Oppositely charged ions attract with strong electrostatic forces.
🧮 Example:
Sodium (Na) + Chlorine (Cl) → Na⁺ + Cl⁻ → NaCl
Each sodium donates one electron to chlorine → both get full outer shells.
📦 Properties of ionic compounds:
- High melting and boiling points (strong ionic bonds).
- Solid state: does not conduct electricity (ions fixed).
- Molten or dissolved: conducts electricity (ions free to move).
💎 Ionic Compounds – Giant Ionic Lattices
Ionic compounds form giant 3D crystal structures of alternating positive and negative ions.
💡 Features:
- Strong forces between ions in all directions.
- Require lots of energy to break (high melting points).
- When dissolved or melted, ions move freely → electrical conductivity.
- Brittle when hit (like charges repel if layers shift).
🧱 Examples:
- Sodium chloride (NaCl)
- Magnesium oxide (MgO)
- Calcium fluoride (CaF₂)
🧪 Summary Table
| Type of Bond | Particles Involved | Example | Key Properties |
|---|---|---|---|
| Ionic | Metal + Non-metal | NaCl | High melting point, conducts when molten |
| Covalent | Non-metal + Non-metal | H₂O | Low melting point, no conductivity |
| Metallic | Metal atoms | Cu | Conducts electricity, malleable, strong |
