Bonding

Question 1

what are giant covalent structures

Answer 1

involves lots of covalent bonds present between several atoms in a regular pattern

Question 2

what is an example of a giant covalent structure and give its properties (5)

Answer 2

Diamonds:
Have a tetrahedral structure
Each carbon atom has made 4 bonds
very very hard - huge network of very strong covalent bonds
very high MP/BP
insoluble in water

Question 3

what are the properties of graphite

Answer 3

Graphite:

Layers/sheets of carbon atoms bonded in hexagonal rings
In graphite, each carbon atom only forms 3 rings

Question 4

why is it important to know that graphite has 3 carbon bonds

Answer 4

In graphite, each carbon atom only forms 3 rings
This leaves one as a delocalised electron, which moves freely within its layer
This delocalised electron can move and carry charge and so it can conduct electricity

Question 5

why is graphite soft (2)

Answer 5

Layers slide over each other very easily making graphite very soft –> weak intermolecular forces between the layers which are easily broken

Question 6

what is graphene and how was it discovered (2)

Answer 6

Graphene = one layer of graphite

it was discovered by putting sticky tape on graphite and ripping it off (leaving just one layer on the tape)

Question 7

what are the properties of graphene (3)

Answer 7

Graphite pieces are really strong for its mass as it has a very low density

Better conductor of electricity than graphite

Most reactive form of carbon

Question 8

what are fullerenes (1)

Answer 8

• carbon atoms can join to make hollow shapes –> fullerene

Question 9

what are the other shapes of fullerenes (4)

Answer 9

C60 fullerene - Buckminster - shape of a sphere
Other shapes: rugby ball, doughnut, onions (spheres within spheres), cones and tubes
Fullerenes are made out of hexagonal rings of carbons
Carbon nanotubes = cylindrical fullerenes

Question 10

what are the properties and uses of fullerenes (4)

Answer 10

Properties:
high tensile strength –> used in reinforcing composite materials –> tennis rackets
high electrical conductivity –> in electrical industry
high SA:V so can be used for drug delivery into body and can also be used as lubricants and catalysts

Question 11

properties of metals and their reasons (4)

Answer 11

Metals:

Very good conductors of heat and electricity - because they have a lot of delocalised electrons within a metal molecule which faciliate the flow of electrons which is electricity
high MP/BP - they electrostatic bonds between the metal atoms are very strong and require a lot of energy to break
Malleable and ductile - because all the atoms are the same size so the layers can slide over each other allowing the metal to bend
Shiny - the atoms are arranged in a regular pattern causing light to reflect of the surface of that molecule in one direction