Questions: Carbon Allotropes: Diamond, Graphite, Fullerenes, Nanotubes, and Graphene
4 questions to test your understanding
Score: 0 / 4
Question 1 Multiple Choice
Why does graphite conduct electricity while diamond does not?
AGraphite contains metal impurities
BGraphite's sp² carbons have delocalized π electrons that move within each layer, while diamond's sp³ carbons have all electrons in localized σ bonds
CDiamond has weaker C–C bonds
DGraphite is an ionic solid
Each graphite carbon uses three electrons in σ bonds and contributes one to a π system spread over the whole sheet. In diamond all four electrons are in localized σ bonds, and a large band gap leaves no mobile carriers.
Question 2 Multiple Choice
Buckminsterfullerene, C₆₀, is built from how many pentagons and hexagons?
A6 pentagons and 20 hexagons
B12 pentagons and 20 hexagons
C12 pentagons and 30 hexagons
D20 pentagons and 12 hexagons
C₆₀ has the shape of a truncated icosahedron, like a soccer ball, with 12 pentagonal and 20 hexagonal faces. Twelve pentagons are exactly what is needed to close a sheet of hexagons into a cage.
Question 3 True / False
Every single-walled carbon nanotube is a metallic conductor.
TTrue
FFalse
Answer: False
For a tube with chiral indices (n,m), it is metallic or nearly so when n − m is a multiple of 3, and semiconducting otherwise. Armchair tubes (n = m) are metallic.
Question 4 Short Answer
How was graphene first isolated as a single layer, and why was this significant?
Think about your answer, then reveal below.
Model answer: In 2004, Andre Geim and Konstantin Novoselov peeled graphite repeatedly with adhesive tape (mechanical exfoliation) until single atomic layers remained. It showed that a stable two-dimensional crystal could exist and opened the study of its unusual electronic properties, recognized by the 2010 Nobel Prize in Physics.
The simplicity of the method made graphene widely available for experiments. Its electrons behave as if massless near the Fermi level, giving very high carrier mobility.