Revision notes · Bonding, structure, and the properties of matter
Structure and bonding of carbon
Diamond4.2.3.1
Definition: Diamond is a giant covalent structure of carbon, where each carbon atom forms four covalent bonds to other carbon atoms.
- •Diamond's rigid, three-dimensional network of strong covalent bonds makes it extremely hard.
- •It has a very high melting point, since many strong covalent bonds must be broken to melt it.
- •Diamond does not conduct electricity, because all outer-shell electrons are used in covalent bonds — none are free to move.
⚠️ Common mistake: Thinking diamond conducts electricity because it is a form of carbon — carbon can conduct (as graphite), but diamond has no free electrons or ions, so it does not.
🧠 Remember: Diamond: 4 bonds each, super hard, no free electrons — doesn't conduct.
Graphite4.2.3.2
Definition: Graphite is a giant covalent structure of carbon, arranged in layers of hexagonal rings, where each carbon atom forms only three covalent bonds.
Graphite's layered structure gives it very different properties from diamond, despite both being pure carbon.
- •Each carbon atom has one delocalised electron not used in bonding, which is free to move along the layers, so graphite conducts electricity.
- •There are only weak forces between the layers, allowing them to slide over each other easily — this makes graphite soft and slippery, useful as a lubricant and in pencils.
- •Graphite has a high melting point, since the covalent bonds within each layer are still strong.
⚠️ Common mistake: Assuming graphite is weakly bonded throughout — the covalent bonds within each layer are just as strong as diamond's; only the forces between layers are weak.
🧠 Remember: Graphite: 3 bonds each, 1 free electron → conducts. Weak forces between layers → soft & slippery.
Graphene and fullerenes4.2.3.3
Definition: Graphene is a single layer of graphite, one atom thick; fullerenes are molecules of carbon atoms arranged as hollow tubes or cages.
Both are newer forms of carbon with useful, unusual properties linked to their structure.
- •Graphene is just one atom thick, so it is used to make new composite materials — it is very strong for its extremely low mass, and conducts electricity well due to delocalised electrons.
- •Fullerenes are based on hexagonal (and sometimes pentagonal/heptagonal) rings of carbon atoms; buckminsterfullerene (C60) is a hollow sphere and was the first fullerene discovered.
- •Carbon nanotubes are cylindrical fullerenes with a very high length-to-diameter ratio, used to reinforce materials (e.g. in tennis rackets) and in nanotechnology and electronics.
⚠️ Common mistake: Thinking graphene is the same as graphite — graphene is just a single layer of graphite, one atom thick, which is what gives it such different (and more extreme) properties.
🧠 Remember: Graphene = 1 layer of graphite. Fullerenes = carbon tubes and cages.
Feel like you’ve got it?
Practise it now →