Structure and bonding of carbon (2.3) (M) Flashcards
Describe the composition of diamond?
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure
3 properties needed
What does diamond’s composition mean for its properties?
- very hard (strong covalent bonds)
- very high melting point (strong covalent bonds)
- doesn’t conduct electricity (no free electrons to carry electrical charge)
Describe the composition of graphite
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings which have no covalent bonds between the layers (weak force of attraction between them)
one electron from each carbon atom is delocalised
How is graphite similar to metals?
They both have delocalised electrons
What are the properties of graphite?
- very high melting/boiling point (strong covalent bonds need lots of energy to overcome)
- strong electrical conductivity (delocalised electron can carry electrical charge)
- softness (weak forces between layers allow them to slide)
What does a model of graphite look like?
What are the uses of graphite?
used as a lubricant (as it is slippery) and in pencils
What are graphenes and fullerene a form of?
forms of carbon
What is graphene?
a single layer of graphite
graphene has (…) covalent bond between atoms
strong
What are the properties of graphene?
- very high melting point
- very strong
- conducts electricity
What are graphene’s uses?
- electronics
- composites
What are composites?
Material made from multiple material with contrasting properties
What are fullerenes?
molecules of carbon atoms with hollow shapes
What are two examples of fullerenes?
buckminsterfullerene and carbon nanotubes
What is the structure of fullerenes?
based on hexagonal rings of carbon atoms but they may also contain rings with five or seven carbon atoms
What was the first fullerene to be discovered?
Buckminsterfullerene
What is the formula of Buckminsterfullerene?
C60
What is the shape of Buckminsterfullerene?
has a spherical shape
What is the difference in terms of structure between graphene and fullerenes?
Graphene has a giant covalent structure, but fullerenes have large molecules.
Buckminsterfullerene has one (…) electron per atom of carbon that can move freely between layers so it can conduct electricity as the delocalised electron carries an electrical charge
delocalised
What are the properties of buckminsterfullerene?
- slippery
- low melting point (weak intermolecular forces)
fullerenes not giant covalent
What does buckminsterfullerene look like?
What are carbon nanotubes?
cylindrical fullerenes with very high length to diameter ratios
2 needed
What are the properties of carbon nanotubes?
- high tensile strength
- high electrical/thermal conductivity
3 needed
What are the uses of carbon nanotubes?
- nanotechnology
- electronics
- specialised materials (e.g. a tennis racket)
3 needed
What are some uses of diamond?
- jewellery
- for cutting tools and blade edges
- to make diamond tipped drill bits
Why is buckminsterfullerene a good lubricant?
- molecules are spherical
- so molecules will role
Why are nanotubes good lubricants?
nanotubes can slide over each other
because there are no covalent bonds between the nanotubes (accept weak intermolecular forces)
2 marks - low demand
Why is diamond hard?
has a giant structure with strong bonds
Why is graphite softer than carbon?
In graphite the layers can slide as there are weak intermolecular forces between the layers
However in diamond, each carbon atom is (strongly/covalently) bonded to 4 others, so atoms are not able to move/slide
4 marks
Why is silicon dioxide suitable for lining furnaces?
Silicon dioxide has a giant covalent structure
with strong bonds
a lot of energy is needed to break these bonds
so silicon dioxide has a high melting point
Why does graphite conduct electricity?
Graphite has delocalised electrons (each carbon atom is covalently bonded to 3 others, so there is 1 delocalised electron per carbon atom)
that can move freely through the whole structure of graphite
and carry a charge
model answer
