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VICChemistryQuick questions
Unit 1: How can the diversity of materials be explained?
Quick questions on Allotropes of carbon and covalent network solids: VCE Chemistry Unit 1
10short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is what an allotrope is?Show answer
Allotropes are different structural forms of the same element in the same physical state. Carbon is the textbook example: the atoms are identical, but the way they bond to one another produces wildly different materials.
What is diamond?Show answer
Each carbon atom forms 4 single covalent bonds to 4 neighbours, arranged tetrahedrally ($109.5^{\circ}$ bond angle). The result is a 3D covalent network lattice with no discrete molecules. Every one of the 4 valence electrons sits in a localised bond.
What is graphite (and graphene)?Show answer
Each carbon atom forms 3 single covalent bonds to 3 neighbours in a flat hexagonal sheet. The 4th valence electron is delocalised within the sheet. Sheets stack on top of one another, held by weak dispersion forces.
What is fullerenes?Show answer
Fullerenes are closed-cage molecules of carbon, the most famous being $C_{60}$ (buckminsterfullerene), a 60-atom sphere of pentagons and hexagons. Each C still forms 3 covalent bonds, but the molecule is a discrete, finite object.
What is carbon nanotubes?Show answer
A carbon nanotube is a graphene sheet rolled into a cylinder, capped at the ends. Very high tensile strength along the axis, conducts along the tube, used in nanoelectronics and composite materials.
What is silicon dioxide ($SiO_2$)?Show answer
The other key network solid for VCE. Every silicon atom is covalently bonded to 4 oxygen atoms and every oxygen to 2 silicons, building a 3D network of $SiO_4$ tetrahedra. It is the structure of quartz and the basis of glass, sand and many minerals.
What is calling graphite "weakly bonded"?Show answer
The in-plane covalent bonds are very strong. Only the layer-to-layer forces are weak.
What is calling fullerene a network solid?Show answer
$C_{60}$ is a molecular solid. The covalent bonds end at each cage.
What is saying diamond is metallic because it is hard?Show answer
Diamond is a covalent network. No delocalised electrons. No conductivity.
What is mixing up graphene and graphite?Show answer
Graphene is one isolated sheet. Graphite is many sheets stacked.