ib chemistry allotropes of carbon

State the electrical conductivity of graphite, diamond, fullerene and graphene.

graphite: good electrical conductor, contains one non-bonded, delocalized electron per atom that gives electron mobility. diamond: non-conductor of electricity; all electrons are bonded so non-mobile. fullerene: a semi-conductor at normal temperature and pressure due to some electron mobility; easily accepts electrons to form negative ions. graphene: very good electrical conductor; one delocalized electron per atom gives electron mobility across the layers.

state the appearance of diamond.

highly transparent, lustrous crystal .

state the appearance of graphite.

non-lustrous ( not shiny), grey crystalline solid.

appearance of fullerene

yellow crystalline solid, soluble in benzene.

state three uses of graphite.

-A dry lubricant ( something that lessens or prevents friction or difficulty.) -electrode rods in electrolysis. -used in pencils

state two uses of fullerene.

-lubricants. -catalysts

state three special properties of graphite.

-soft and slippery due to slippage of layers over each other -brittle -the most stable allotrope of carbon

state three special properties of diamond.

-the hardest known natural substance. -it cannot be scratched by anything. -very high melting point.

state three special properties of graphene.

-the thickness of one atom so the thinnest material to ever exist. -100 times stronger than steel. -very flexible.

state three special properties of fullerene.

-very light and strong. -reacts with k to make superconducting crystalline material. -low melting point.

outline three uses of graphene.

TEM grids touch screens electronic devices

structure of fullerene

Each carbon atom is bonded in a sphere of 60 atoms, consisting of 12 pentagons and 20 hexagons. Structure is a closed spherical cage in which each carbon atom is bonded to 3 others. (Note it is note a giant molecule as it has a fixed formula.)

structure of graphene

Each carbon atom is covalently bonded to 3 others, as in graphite, forming hexagons with bond angles of 120. But it is a single layer, so exits as a two-dimensional material only. It is often described as a honeycomb or chicken wire structure.

structure of graphite

Each carbon atom is covalently bonded to 3 others, forming hexagons in parallel layers with bond angles of 120. The layers are held only by weak London dispersion forces so they can slide over each other.

structure of diamond

Each carbon atom is covalently bonded to 4 others tetrahedrally arranged in a regular repetitive pattern with bond angles of 109.5

which is the best thermal conductor and which is not?

Graphene is the best thermal conductor known, even better than diamond. Graphite is not a good conductor.