allotropes of carbon

Question 1

why is diamond hard?

Answer 1

it has a giant covalent structure and each atom forms 4 covalent bonds, these bonds are extremely strong

Question 2

why does diamond have a high melting point?

Answer 2

the strong covalent bonds take a lot of energy to break

Question 3

why does diamond not conduct electricity?

Answer 3

it has no free electrons or ions

Question 4

how many covalent bonds does each carbon atom form in graphite?

Answer 4

three

Question 5

what shape do the atoms create in graphite?

Answer 5

hexagon

Question 6

why is graphite soft and slippery?

Answer 6

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

Question 7

why does graphite have a high melting point?

Answer 7

the covalent bonds within the layers require large amounts of energy to break

Question 8

why does graphite conduct electricity?

Answer 8

-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

Question 9

graphene

Answer 9

a sheet of carbon atoms joined together in hexagons

Question 10

why is graphene strong?

Answer 10

it has a network of covalent bonds

Question 11

fullerenes

Answer 11

molecules of carbon, shaped like closed tubes of hollow balls

Question 12

buckminsterfullerene, what shape is it?

Answer 12

C₆₀, forms a hollow sphere

Question 13

how many hexagons and pentagons does buckminsterfullerene contain?

Answer 13

20 hexagons, 12 pentagons

Question 14

why are fullerenes used to deliver drugs around the body?

Answer 14

they can cage other molecules as the structure forms around another atom

Question 15

why are fullerenes good as industrial catalysts?

Answer 15

they have a huge surface area

Question 16

why do fullerenes make good lubricants?

Answer 16

They form nanotubes which have a high length to diameter ratio and can conduct electricity and heat

Question 17

why is carbon good at forming giant covalent structures?

Answer 17

it can make 4 strong covalent bonds as it is in group 4

Question 18

list 4 properties of diamond

Answer 18

-insoluble in water
-hard
-doesn’t conduct electricity
-high melting/boiling points

Question 19

describe how the atoms are bonded together in diamond

Answer 19

-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

Question 20

list 5 properties of graphite

Answer 20

-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

Question 21

describe how the atoms are bonded together in graphite?

Answer 21

-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

Question 22

why does diamond not conduct but graphite does?

Answer 22

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

Question 23

why is graphite softer than diamond?

Answer 23

-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

Question 24

what property makes graphene able to be added to composite materials and why?

Answer 24

it is light so can be added to improve their strength without adding much weight

Question 25

4 properties of nanotubes

Answer 25

-high length to diameter ratio
-high tensile strength
-can conduct
-large surface area

Question 26

list 4 uses of buckminsterfullerene

Answer 26

-drug delivery into body
-lubricants
-catalysts
-hollow cages to trap molecules

Question 27

4 uses of carbon nanotubes

Answer 27

-catalysts
-nanotechnology
-reinforcing materials
-semi conductors in electrical circuits