VS
Diamond & Graphite
World C — Carbon Chemistry
29.A — STRUCTURAL GEOMETRY
R29.01 Diamond sp³ Lattice
- Giant 3D covalent network.
- Tetrahedral geometry ($109.5^\circ$).
- Extremely rigid and interlocked.
R29.02 Graphite sp² Layers
- 2D hexagonal planar sheets.
- Trigonal planar geometry ($120^\circ$).
- One delocalized electron per carbon.
154 pm
142 pm
R29.03 Bond Lengths
- Diamond C-C: 154 pm (Pure single bond).
- Graphite C-C: 142 pm (Partial double bond).
- Graphite intralayer bonds are stronger!
R29.04 Interlayer Forces
- Graphite layers held by weak Van der Waals forces.
- Distance between layers is huge (340 pm).
- Allows layers to slide easily.
29.B — PHYSICAL PROPERTIES
R29.05 Hardness
- Diamond: Hardest known natural substance (Mohs 10).
- Graphite: Soft, slippery, leaves marks (Mohs 1-2).
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R29.06 Electrical Conductivity
- Diamond: Perfect insulator (no free e⁻).
- Graphite: Excellent conductor (delocalized $\pi$ e⁻).
R29.07 Thermal Conductivity
- Diamond: Highest thermal conductivity of any bulk material (rigid lattice transfers vibrations).
- Graphite: Anisotropic (conducts well along layers, poorly across).
R29.08 Density & Refraction
- Diamond: Very dense (3.5 g/cm³), highly refractive (brilliant).
- Graphite: Less dense (2.2 g/cm³), opaque and black.
29.C — THERMO & TRANSFORMATION
DIA
GRA
R29.09 Stability
- Graphite is the thermodynamically stable form at STP.
- Diamond is metastable (slowly degrading to graphite, but takes billions of years).
R29.10 Synthetic Conversion
- High Pressure, High Temperature (HPHT) required to turn Graphite → Diamond.
- Forces 2D layers to buckle into 3D sp³ bonds.
→
CO₂
←
R29.11 Combustion
- Both burn in pure oxygen at high temps.
- Both yield exactly the same product: $CO_2$ gas.
- Leaves zero ash (proving they are pure Carbon).
R29.12 Chemical Reactivity
- Diamond is chemically inert (resists acids/bases).
- Graphite is slightly more reactive (can form intercalation compounds).
29.D — INDUSTRIAL APPLICATIONS
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R29.13 Cutting & Abrasives
- Diamond tip drills for rock boring.
- Saw blades for cutting concrete and glass.
- Polishing pastes for high-precision optics.
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R29.14 Lubrication & Pencils
- Graphite powder used as dry lubricant (machines running at high temps).
- Mixed with clay to form pencil "lead".
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R29.15 Electrodes & Batteries
- Graphite rods used in dry cells and electrolysis.
- Primary anode material in Lithium-Ion batteries.
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R29.16 Jewelry & Optics
- High dispersion splits white light into colors (fire).
- Used in high-power laser windows due to thermal conductivity.