Diamond, Graphite, Graphene, Fullerenes & Nanoparticles
Giant covalent structures consist of billions of non-metal atoms joined together in a continuous three-dimensional network by strong covalent bonds, giving substances like diamond, graphite, and silicon dioxide extremely high melting points. Carbon forms several structural allotropes depending on whether each carbon atom forms four covalent bonds (diamond) or three covalent bonds with one delocalised electron (graphite, graphene, and fullerenes). Examiners frequently compare diamond and graphite, test the applications of fullerenes, and require surface area to volume ratio (SA:V) calculations for Triple Science nanoparticles.
- Diamond & Silicon Dioxide (SiO₂)
- Giant covalent structures. In diamond, each carbon atom forms 4 strong covalent bonds in a rigid tetrahedral network. Properties: extremely hard (used in cutting tools), very high melting point (~3550°C, as millions of strong covalent bonds must be broken), and does not conduct electricity (no delocalised electrons). Silicon dioxide (silica/sand) has a similar giant tetrahedral covalent network of silicon and oxygen atoms.
- Graphite Structure & Properties
- Giant covalent structure where each carbon atom forms 3 strong covalent bonds, creating flat hexagonal layers. 1. High melting point (many strong covalent bonds within layers). 2. Soft and slippery (weak forces between layers allow layers to slide). 3. Conducts electricity and heat (1 delocalised electron per carbon atom moves freely along the layers).
- Graphene
- A single layer of graphite (a 2D sheet of hexagonally arranged carbon atoms just one atom thick). It has a very low density, is ~200 times stronger than steel due to its unbroken network of strong covalent bonds, and is an excellent electrical and thermal conductor via its delocalised electrons.
Diamond, Graphite, Graphene, Fullerenes & Nanoparticles: 3D Molecular, Lattice, DNA & Vector Explorer
Drag directly on the 3D model to rotate it through any angle, or switch tabs to inspect VSEPR bond angles, crystal lattices, DNA base pairing, and 3D space diagonals.
Giant Ionic Lattice (Sodium Chloride, NaCl)
- Bonding Type:
- Strong electrostatic attraction between oppositely charged Na⁺ and Cl⁻ ions in all directions
- Melting / Sublimation Point:
- High (801°C): large energy needed to overcome many strong electrostatic attractions
- Electrical Conductivity:
- Insulator when solid (ions fixed in lattice); conducts when molten or aqueous (mobile ions carry charge)
Never write 'delocalised electrons' for an ionic compound. Solid NaCl does not conduct because its ions are locked in fixed positions; melting or dissolving frees the ions to move.
Key Concepts & Exam Definitions (6)
- Diamond & Silicon Dioxide (SiO₂)
- Giant covalent structures. In diamond, each carbon atom forms 4 strong covalent bonds in a rigid tetrahedral network. Properties: extremely hard (used in cutting tools), very high melting point (~3550°C, as millions of strong covalent bonds must be broken), and does not conduct electricity (no delocalised electrons). Silicon dioxide (silica/sand) has a similar giant tetrahedral covalent network of silicon and oxygen atoms.
- Graphite Structure & Properties
- Giant covalent structure where each carbon atom forms 3 strong covalent bonds, creating flat hexagonal layers. 1. High melting point (many strong covalent bonds within layers). 2. Soft and slippery (weak forces between layers allow layers to slide). 3. Conducts electricity and heat (1 delocalised electron per carbon atom moves freely along the layers).
- Graphene
- A single layer of graphite (a 2D sheet of hexagonally arranged carbon atoms just one atom thick). It has a very low density, is ~200 times stronger than steel due to its unbroken network of strong covalent bonds, and is an excellent electrical and thermal conductor via its delocalised electrons.
- Fullerenes: Buckminsterfullerene (C₆₀) & Nanotubes
- Molecules of carbon atoms with hollow shapes (mainly hexagonal rings, plus pentagonal/heptagonal rings). Buckminsterfullerene (C₆₀) is the first fullerene discovered: a spherical molecule with weak intermolecular forces between spheres (low melting point, slippery lubricant, and cages for targeted drug delivery). Carbon nanotubes are cylindrical fullerenes with high tensile strength and electrical conductivity, used to reinforce tennis rackets and in microelectronics.
- Nanoparticles (1 nm to 100 nm) (Triple Science)
- Nanoscience studies structures that are 1 to 100 nanometres (1 x 10⁻⁹ m to 1 x 10⁻⁷ m) in size, containing only a few hundred atoms. Fine particles (PM₂.₅) have diameters between 100 and 2,500 nm; coarse particles (PM₁₀, dust) have diameters between 2,500 nm and 10,000 nm (1 x 10⁻⁵ m).
- Uses & Risks of Nanoparticles (Triple Science)
- Because of their huge surface area to volume ratio (SA:V), nanoparticles are used in: catalysts (smaller quantities needed), medicine (targeted drug delivery into cells), cosmetics/sunscreens (titanium dioxide/zinc oxide block UV light without leaving white marks), silver-coated antibacterial wound dressings/deodorants, and electronics. Risks: they may be inhaled into lungs, catalyse harmful reactions in the body, or bind toxic pollutants in the environment.
Quick-Fire Flashcards (6)
Click any card to check the answer, then mark it as Known to track your progress.
Why does diamond have a very high melting point?
Explain why graphite conducts electricity (3 mark points).
Why does Buckminsterfullerene (C₆₀) have a much lower melting point than diamond or graphite?
State three uses of fullerenes and carbon nanotubes.
If the side length of a cube decreases by a factor of 10 (e.g., from 10 nm to 1 nm), what happens to its surface area to volume ratio (SA:V)?
Give one advantage and one potential risk of using titanium dioxide nanoparticles in sunscreens.
Exam-Style Questions & Mark Schemes (4)
Write or think through your answer first, then click Check Mark Scheme to see the exact points examiners award marks for.
- Q1
Compare the structure and bonding of diamond and graphite, and use these differences to explain why diamond is extremely hard and an electrical insulator, whereas graphite is soft and an electrical conductor. [6 marks]
Click “Check Mark Scheme” to compare your answer, 1. Both diamond and graphite are giant covalent structures made entirely of carbon atoms [1 mark]. 2. In diamond, each carbon atom forms 4 strong covalent bonds with 4 other carbon atoms in a rigid 3D tetrahedral lattice; because there are no layers that can slide, diamond is extremely hard [1 mark]. 3. Because all 4 outer-shell electrons of each carbon atom in diamond are fixed in covalent bonds, there are no delocalised electrons to move and carry charge, so diamond does not conduct electricity [1 mark]. 4. In graphite, each carbon atom forms only 3 strong covalent bonds, creating flat hexagonal layers of carbon atoms [1 mark]. 5. There are only weak intermolecular forces between the layers in graphite, allowing the layers to slide over one another easily, making graphite soft and slippery [1 mark]. 6. The 4th outer-shell electron of each carbon atom in graphite is delocalised and free to move along the layers to carry electrical charge, so graphite conducts electricity [1 mark].
- Q2
Silicon dioxide (SiO₂) has a melting point of 1,710°C, whereas carbon dioxide (CO₂) is a gas at room temperature with a sublimation point of -78.5°C. Explain this difference in terms of structure and bonding. [4 marks]
Click “Check Mark Scheme” to compare your answer, 1. Silicon dioxide has a giant covalent structure where every silicon and oxygen atom is joined by strong covalent bonds in a continuous 3D lattice [1 mark]. 2. A very large amount of thermal energy is needed to break these millions of strong covalent bonds, giving SiO₂ a high melting point [1 mark]. 3. Carbon dioxide has a simple molecular structure consisting of small, discrete CO₂ molecules [1 mark]. 4. There are only weak intermolecular forces between the CO₂ molecules, which require very little energy to overcome (the strong C=O covalent bonds do not break) [1 mark].
- Q3
Explain how the structure and properties of carbon nanotubes make them suitable for reinforcing composite materials in sports equipment and for use in microelectronics. [4 marks]
Click “Check Mark Scheme” to compare your answer, 1. Carbon nanotubes are cylindrical fullerenes made of carbon atoms arranged in hexagonal rings joined by strong covalent bonds [1 mark]. 2. They have a very high length-to-diameter ratio and high tensile strength (they do not break easily when stretched), so they reinforce composite materials without adding much mass/weight [1 mark]. 3. Like graphite, each carbon atom forms 3 covalent bonds, leaving 1 delocalised electron per carbon atom [1 mark]. 4. These delocalised electrons can move rapidly along the tube to conduct electricity, making nanotubes ideal for microelectronic circuits and semiconductors [1 mark].
- Q4
A bulk cube of silver has sides of length 2 cm, while a silver nanoparticle cube has sides of length 20 nm. Calculate the surface area to volume ratio (SA:V) of the nanoparticle in nm⁻¹, and explain why silver nanoparticles are used in antibacterial wound dressings rather than bulk silver. (Triple Science) [4 marks]
Click “Check Mark Scheme” to compare your answer, 1. For the 20 nm cube: Surface area = 6 x (20 x 20) = 2,400 nm²; Volume = 20 x 20 x 20 = 8,000 nm³ [1 mark]. 2. SA:V ratio = 2,400 / 8,000 = 0.3 nm⁻¹ (or 3:10) [1 mark]. 3. Nanoparticles have an extremely large surface area to volume ratio compared to bulk silver (where SA:V is 3 cm⁻¹ = 3 x 10⁻⁷ nm⁻¹) [1 mark]. 4. A much greater proportion of silver atoms are exposed on the surface to release antibacterial silver ions, so a much smaller, cheaper mass of silver is needed to kill bacteria effectively [1 mark].
Common Exam Questions (4)
Why does graphite conduct electricity whereas diamond does not?
Each carbon atom in systemic outer shell has 4 electrons. In diamond, each carbon atom forms 4 strong covalent bonds with 4 other carbon atoms, so there are no free electrons. In graphite, each carbon atom forms only 3 covalent bonds with 3 other carbon atoms; the 4th outer electron is delocalised and free to move between the hexagonal layers to carry electrical charge.
Why is graphite soft and slippery, making it useful as a lubricant and in pencils?
Graphite is arranged in flat hexagonal layers of carbon atoms. While the covalent bonds within each layer are very strong, there are only weak intermolecular forces between the layers, allowing the layers to slide over each other easily and rub off onto paper.
What is the difference between graphene, buckminsterfullerene (C₆₀), and carbon nanotubes?
Graphene is a single flat layer of graphite (one atom thick) that is extraordinarily strong and conducts electricity. Fullerenes are molecules of carbon atoms with hollow shapes based on hexagonal rings: Buckminsterfullerene (C₆₀) is a hollow sphere used for drug delivery and lubricants, while carbon nanotubes are cylindrical fullerenes with a very high length-to-diameter ratio used in electronics and composite materials.
Why do nanoparticles have different properties from the same material in bulk form?
Nanoparticles have diameters between 1 nm and 100 nm (1 x 10⁻⁹ m to 1 x 10⁻⁷ m). As particle size decreases by a factor of 10, the surface area to volume ratio (SA:V) increases by a factor of 10. This huge fraction of atoms exposed on the surface makes nanoparticles far more effective catalysts in much smaller quantities.
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