Chapter 3

Question 1

Ionic bonding

Answer 1

Between a metal and a non-metal
Transfer of electrons
So both gain a full outer shell
Strong electrostatic forces of attraction acting in all directions - high melting and boiling point
Giant 3D lattice structure
Cannot conduct electricity when solid - ions cannot move
Can conduct electricity when molten / dissolved - ions are free to move
When dissolved in water, lattice is split up by water molecules

Question 2

Covalent bonding

Answer 2

Between 2 non-metals - neither can give away electrons
Sharing of a pair of electrons
So both gain a full outer shell
Double bonds possible
Simple - low melting / boiling points, don’t conduct electricity, even when molten, unless they react with water to form aqueous ions
Giant - connected to lots of atoms, high melting / boiling points, rigid 3D lattice (intermolecular forces increase with the size of the molecule), insoluble in water

Question 3

Metallic bonding

Answer 3

Between 2 metals
Loss of electrons
So gain a full outer shell
Sea of delocalised electrons holding positive ions in place (electrostatic forces of attraction)
Atoms in a pure metal are able to slide over each other - regularly arranged layers
Alloys are much harder - their atoms are different sizes, so they cannot slide over each other

Question 4

Polymers

Answer 4

Made up of many small, reactive molecules e.g. poly(ethene)

Question 5

Fullerenes

Answer 5

Large hollow structures
Cylindrical nanotubes - high tensile strength (good for reinforcing composite materials), high electrical and thermal conductivity (used in the electronics industry)

Question 6

Graphene

Answer 6

A single layer of graphite, one atom thick
Extremely good electrical and thermal conductor
Low density
Most reactive form of carbon
Very strong for its mass

Question 7

Nanoparticles

Answer 7

1x10^-9 = 1 nanometre
Highly reactive (high SA:V ratio - lots of particles exposed at the surface of a substance)
Uses: cosmetics e.g. suncream, face creams and deodorants (absorbed deeper into the skin); medicine e.g. delivery of drugs to specific parts of the body; silver nanoparticles used to inhibit the growth of organisms; catalysts
Concerns: violent explosion if exposed to a spark nearby (very reactive); health hazards if they find their way into the atmosphere