Ionic

Particles are oppositely charged ions

Occurs in compounds formed from metals combined with non metals.

Covalent

Particles are atoms that share pairs of electrons

Occurs in most non metallic elements and in compounds of non metals.

Metallic

Particles are atoms which share delocalised electrons

Occurs in metallic elements and alloys.

Electrons are transferred so that all atoms have a noble gas configuration (full outer shells).

Metal atoms lose electrons and become positively charged ions

​

Group 1 metals form +1 ions

Group 2 metals form +2 ions

Non metals atoms gain electrons to become negatively charged ions

​

Group 6 non metals form -2 ions

Group 7 non metals form -1 ions

Dot and cross diagram

​

​

​

​

Giant structure

​

​

​

​

​

​

​

​

Structure

• Held together by strong electrostatic forces of attraction between oppositely charged ions
• Forces act in all directions in the lattice

High melting and boiling points

Large amounts of energy needed to break the bonds.

Do not conduct electricity when solid

Ions are held in a fixed position in the lattice and cannot move.

Do conduct electricity when molten or dissolved

Lattice breaks apart and the ions are free to move.

Giant structure of atoms arranged in a regular pattern

​

Electrons in the outer shell of metal atoms are delocalised and free to move through the whole structure. This sharing of electrons leads to strong metallic bonds.

Good conductors of electricity

Delocalised electrons carry electrical charge through the metal.

Good conductors of thermal energy

Energy is transferred by the delocalised electrons.

High melting and boiling points

This is due to the strong metallic bonds.

Pure metals can be bent and shaped

Atoms are arranged in layers that can slide over each other.

Alloys

Mixture of two or more elements at least one of which is a metal

Harder than pure metals because atoms of different sizes disrupt the layers so they cannot slide over each other.

s

solid

l

liquid

g

gas

Solid, liquid, gas

Melting and freezing happen at melting point, boiling and condensing happen at boiling point.

​

​

​

​

The amount of energy needed for a state change depends on the strength of forces between particles in the substance.

(HT only)

Limitations of simple model:

• There are no forces in the model
• All particles are shown as spheres
• Spheres are solid

Pure metal Alloy

Usually gases or liquids

Covalent bonds in the molecule are strong but forces between molecules (intermolecular) are weak

Low melting and boiling points.

Due to having weak intermolecular forces that easily broken.

Do not conduct electricity.

Due to them molecules not having an overall electrical charge.

Larger molecules have higher melting and boiling points.

Intermolecular forces increase with the size of the molecules.

Diamond, graphite, silicon dioxide

Very high melting points

Lots of energy needed to break strong, covalent bonds.

Atoms share pairs of electrons

Can be small molecules

e.g. ammonia

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

​

Can be giant covalent structures

e.g. polymers

​

​

​

​

​

​

Each carbon atom is bonded to four others

​

Very hard.

Rigid structure.

Very high melting point.

Strong covalent bonds.

Does not conduct electricity.

No delocalised electrons.

Each carbon atom is bonded to three others forming layers of hexagonal rings with no covalent bonds between the layers

​

Slippery.

Layers can slide over each other.

Very high melting point.

Strong covalent bonds.

Does conduct electricity.

Delocalised electrons between layers.

Very large molecules

Solids at room temperature

Atoms are linked by strong covalent bonds.

​

Graphene

​

​

​

​

​

Single layer of graphite one atom thick

Excellent conductor.

Contains delocalised electrons.

Very strong.

Contains strong covalent bonds.

Fullerenes

​

Buckminsterfullerene, C₆₀

First fullerene to be discovered.

Hexagonal rings of carbon atoms with hollow shapes. Can also have rings of five (pentagonal) or seven (heptagonal) carbon atoms.

Carbon nanotubes

​

​

​

​

​

​

Very thin and long cylindrical fullerenes

Very conductive.

Used in electronics industry.

High tensile strength.

Reinforcing composite materials.

Large surface area to volume ratio.

Catalysts and lubricants.

Nanoparticles

Between 1 and 100 nanometres (nm) in size

1 nanometre (1 nm) = 1 x 10^-9 metres

(0.000 000 001m or a billionth of a metre).

Healthcare,

cosmetics,

sun cream,

catalysts,

deodorants,

electronics.

Nanoparticles may be toxic to people. They may be able to enter the brain from the bloodstream and cause harm.