Chapter 7 - Carbon

7.1 Carbon Lattices

Carbon is a unique non-metal that can bond to itself in different ways, forming allotropes — different structural forms of the same element with very different physical properties.

Key Facts about Carbon

• 11th most abundant element in the universe and a vital component of all living things.

• Has three main isotopes: ¹²C (98.9%), ¹³C, ¹⁴C.

• Can form single, double, and triple covalent bonds.

• Exists in multiple allotropes: diamond, graphite, graphene, fullerenes, and amorphous carbon.

Allotropes of Carbon

Diamond – Covalent Network Lattice

• Continuous 3D network of strong single covalent bonds.

• Each carbon atom is bonded to four others in a tetrahedral arrangement.

• No small discrete molecules → no weak intermolecular forces.

• Explains:

  • Extreme hardness

  • Very high sublimation point

  • Non-conductor of electricity (no free electrons or ions)

  • Excellent thermal conductor

Uses: Jewellery (sparkle + hardness) and industrial cutting/drilling tools.

Graphite – Covalent Layer Lattice

• Strong covalent bonds within each layer (each C bonded to 3 others).

• Weak dispersion forces between layers → layers can slide over each other.

• One delocalised electron per carbon atom → conducts electricity.

• Explains:

  • Soft and slippery (used as lubricant)

  • Conductive (used in electrodes)

  • High thermal stability

Uses: Pencils (mixed with clay), lubricants, battery electrodes, reinforcing fibres in composites.

Amorphous Carbon

• Irregular arrangement of carbon atoms.

• Examples: charcoal, soot, carbon black.

• Cheaper and used as filler, pigment, or adsorbent.

Other Covalent Network Lattices (Extension)

Silica (SiO₂) – Silicon dioxide (quartz, sand, glass)

• Each Si atom bonded tetrahedrally to 4 O atoms.

• Each O atom bonded to 2 Si atoms.

• Forms a very hard, high-melting covalent network lattice.

• Major component of sand, glass, and many minerals.

Summary of Bonding in Carbon Allotropes

• Diamond: Giant 3D covalent network → very hard, non-conductive.

• Graphite: Layered covalent network with delocalised electrons → soft, conductive.

• Properties are determined by the arrangement and strength of covalent bonds and the presence/absence of free electrons.

7.2 Carbon Nanomaterials

These are recently discovered allotropes of carbon (since the 1970s–2000s) that exist at the nanoscale. They have extraordinary properties due to their structure and very high surface-area-to-volume ratio.

Fullerenes

• Discovered in the 1980s by Richard Smalley, Harry Kroto, and Robert Curl (Nobel Prize winners).

• Spherical molecules made of carbon atoms arranged in pentagons and hexagons (like a soccer ball).

• Most common: Buckminsterfullerene (C₆₀) — 60 carbon atoms.

• Each carbon forms three covalent bonds, leaving delocalised electrons (similar to graphite).

Properties: Strong, can conduct electricity, chemically stable.
Uses/Potential: Photovoltaic (solar) cells, drug delivery, lubricants.

Graphene

• A single layer of carbon atoms arranged in a hexagonal lattice (one atom thick).

• Essentially a single layer of graphite.

• Isolated in 2004.

Properties:

• Extremely strong and tough (stronger than steel).

• Excellent electrical and thermal conductor.

• Flexible, transparent, and very thin.

• Every carbon atom is available for reaction from both sides.

Potential Uses:

• Computer chips and circuits (faster than silicon).

• Desalination membranes.

• Strong, lightweight composites.

• Flexible solar cells and touchscreens.

• Electrodes and batteries.

Carbon Nanotubes

• Formed by rolling a sheet of graphene into a hollow cylinder (tube), capped with half a fullerene.

• Can be single-walled or multi-walled.

• Extremely long compared to their diameter (can be millions of times longer).

Properties:

• Strongest material known (up to 300 times stronger than steel).

• Excellent electrical conductivity (some metallic, some semi-conducting).

• Outstanding thermal conductivity.

• Very lightweight and flexible.

Potential Applications:

• Super-strong composites (sports equipment, aircraft, cars).

• Nanowires and miniature electronics.

• High-performance batteries and supercapacitors.

• Space elevator cables (theoretical).

Real-World Examples & Future Potential

• Volvo Concept Car: Uses carbon nanotube sheets for body panels (lighter, stronger, and can act as a battery).

• Solar Impulse-2: Solar-powered aircraft that flew around the world using lightweight carbon nanomaterials and solar cells.

Summary of Carbon Allotropes

Key Idea: The way carbon atoms are arranged (bonding and structure) determines the properties — from soft graphite to the strongest nanomaterials.