Allotropes of carbon

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Share this infographic with your students, download the poster for your classroom and get students using their knowledge with the accompanying activity

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This infographic is designed to be displayed as a poster in the classroom (though it could also be displayed on a projector or printed out as a handout). Use the accompanying fact sheet and differentiated flash card activity to explore the different properties and uses of four allotropes of carbon – diamond, graphite, graphene and buckminsterfullerene. Learners extract information from the infographic to complete the cards.

Poster as pdf (A4 single pages or A3 one page)
Fact sheet as MS Word and pdf
Flash cards for age range 14–16 as MS Word or pdf
Flash card answers as MS Word or pdf

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Some elements are able to exist in different structural forms, known as allotropes. Carbon does this very well because of its ability to form bonds with other neighbouring carbon atoms – something called catenation.

The way in which carbon atoms are connected to each other makes a big difference to the physical, chemical and electronic properties of the material. Some carbon allotropes have been known for a long time; others have been discovered more recently.

Diamond

Structure

Diamond has a tetrahedral structure. Each carbon atom is connected to four other carbon atoms by a covalent bond to form a giant crystal lattice.

1_Diamond_Structure

Used for …

drill bits in oil exploration and for slicing through concrete
jewellery: naturally-made diamonds are of higher purity and very expensive!

Because …

of its tetrahedral structure, diamond is one of the hardest known materials
it has a high refractive index, light is reflected internally, so it sparkles
all diamond’s electrons are used to create the bonding lattice, leaving none spare, it’s a poor conductor of electricity

Source: © Dan Bright

Source: © Dan Bright

4027°C – That’s how much you have to heat diamond to break all its bonds and liquefy it into molten carbon. It’s so hard to change into a gas because of its tetrahedral structure.

3600°C – Heat graphite to this temperature to sublime it. That’s how much energy it takes to break its covalent bonds. Perfect for nuclear reactor cores.

Graphite

Structure

Each carbon atom is covalently bonded to just three others, leaving one electron spare. This results in atoms arranged in flat layers of hexagons, between which is a soup of free, delocalised electrons that’s made up from the spare electrons.

An illustration showing the hexagonal layers of the molecular structure of Graphite

Used for …

pencil leads
nuclear reactor cores, to stop or slow the nuclear reaction

Because …

its layer-like structure makes it soft and flaky, as a pencil it leaves marks on your paper
so much energy is needed break the covalent bonds, graphite is tough enough to be used in a nuclear reactor
of its soup of spare electrons, graphite is a very good conductor of electricity

Graphene

Graphene was a theoretical concept before it was isolated and studied in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester, who were awarded the Nobel prize in physics in 2010 for their discovery. It’s the thinnest, lightest, strongest, most stretchy material we’ve ever created.

Structure

Think of graphene as a single layer extracted from graphite. In its hexagonal lattice, each carbon is bonded with three others, leaving a spare electron.

An illustration showing the molecular hexagonal structure of Graphene

Used for …

solar cells that are both transparent and flexible
smart windows that can control heat and light transmittance
electronic displays

Because …

of its spare electrons graphene is an excellent conductor of electricity and heat

Source: © Dan Bright

1 g – that's how much a single sheet of graphene the size of a football pitch would weigh!

In 1985, a team headed by Professor Sir Harry Kroto from the University of Sussex discovered and named C₆₀ or buckminsterfullerene.

Fullerenes

Until 1985 it was thought there were only two allotropes of carbon: diamond and graphite. But scientists thought they had detected the presence of another form of carbon in space. That mysterious new allotrope is C₆₀, or buckminsterfullerene. Other fullerenes exist too, like C₇₀, as well as ellipsoids and tubes.

Structure

Buckminsterfullerene’s spherical structure comprises 60 carbon atoms arranged as 20 hexagons and 12 pentagons. The same shape as a football – which is why C₆₀ is also sometimes called a ‘buckyball’.