allotropes of carbon Flashcards
why is diamond hard?
it has a giant covalent structure and each carbon atom forms 4 covalent bonds with other carbon atoms, these bonds are extremely strong
why does diamond have a high melting point?
the strong covalent bonds take a lot of energy to break
why does diamond not conduct electricity?
it has no free electrons or ions
how many covalent bonds does each carbon atom form in graphite?
three
what shape do the atoms create in graphite?
hexagon
why is graphite soft and slippery?
atoms can slide over each other as there are no strong covalent bonds between the layers, they are only held together by weak intermolecular forces
why does graphite have a high melting point?
the covalent bonds within the layers require large amounts of energy to break
why does graphite conduct electricity?
- atoms on each layer arranged in hexagons
- each carbon atom only forms 3 covalent bonds
- leaving one spare delocalised electron on each atom
- free to move along layers
- move through structure carrying charge
graphene
a sheet of carbon atoms joined together in hexagons
why is graphene strong?
it has a network of covalent bonds
what are fullerenes?
molecules of carbon atoms with hollow shapes
buckminsterfullerene, what shape is it?
C₆₀, forms a hollow sphere
how many hexagons and pentagons does buckminsterfullerene contain?
20 hexagons, 12 pentagons
why are fullerenes used to deliver drugs around the body?
they can cage other molecules as the structure forms around another atom
why are fullerenes good as industrial catalysts?
they have a huge surface area
why do fullerenes make good lubricants?
They form nanotubes which have a high length to diameter ratio and can conduct electricity and heat
why is carbon good at forming giant covalent structures?
it can make 4 strong covalent bonds as it is in group 4
list 4 properties of diamond
- insoluble in water
- hard
- doesn’t conduct electricity
- high melting/boiling points
describe how the atoms are bonded together in diamond
- carbon atoms covalently bonded together strongly
- each carbon atom is joined to 4 other carbon atoms so makes a giant covalent structure
- all covalent bonds in diamond are identical
list 4 properties of graphite
- conduct electricity
- slippery as there are no covalent bonds between layers, only intermolecular forces
- high melting point
- 4th electron not used so delocalised between layers
describe how the atoms are bonded together in graphite?
- flat layers of carbon in hexagons
- each layer is joined by strong covalent bonds to only 3 other carbon atoms
- strong bonds in layer, weak intermolecular forces between layers
why does diamond not conduct but graphite does?
diamond has no free electrons as all the electrons are used in bonding unlike graphite which has 1 electron delocalised per atom, allowing it to carry charge through the structure
why is graphite softer than diamond?
- graphite contains layers of graphene which can slide over each other
- weak intermolecular forces between layers
- in diamond each carbon atom is covalently bonded to 4 others
- therefore atoms are unable to move or slide
what property makes graphene able to be added to composite materials and why?
it is light so can be added to improve their strength without adding much weight
4 properties of nanotubes
- high length to diameter ratio
- high tensile strength
- can conduct
- large surface area
list 4 uses of buckminsterfullerene
-drug delivery into body
-lubricants
-catalysts
-hollow cages to trap molecules
4 uses of carbon nanotubes
- catalysts
- nanotechnology
- reinforcing materials
- semi conductors in electrical circuits
what are carbon nanotubes?
cylindrical fullerenes with very high length to diameter ratios
3 uses of carbon nanotubes
electronics, materials, nanotechnology
