Ionic Compounds

Ionic compounds have a regular lattice structure:

• The ions form a closely packed regular lattice and there are very strong electrostatic forces of attraction between oppositely charged ions.
• The electrostatic atrraction between the oppositely charged ions is ionic bonding.

Ionic compounds all have similar properties:

• 1) They all have high melting points and high boiling points because of the many strong bonds between the ions. 
• 2) When they're solid, the compunds can't conduct electricity.
• 3) When ionic compunds melt, the ions are free to move, so they'll carry an electric current.
• 4) Ionic compounds also dissolve in water and they'll carry an electric current then.

Covalent bonds- sharing electrons:

• 1) When non-metal atoms bonds together, they share pairs of electrons to make covalent bonds.
• 2) Each single covalent bond provides one extra shared electron for each atom.
• 3) Covalent bonding happens in compounds of non-metals and in non-metal elements.

Properties of simple molecular substances:

• 1) The atoms within the molecules are held together by very strong covalent bonds. By contrast, the forces of attraction between the molecules are very weak.
• 2) They have very low melting and boiling points because the intermolecular forces are weak and so the molecules can be easily parted from each other.
• 3) Most molecular substances are gases or liquids at room temperature.
• 4) Molecular compounds don't conduct electricity, because they aren't charged so there are no free electrons or ions.

Diamond:

• Diamond is made up of carbon atoms that each form 4 covalent bonds which makes diamomnd really hard.
• These strong covalent bonds are hard to break which gives diamond a high melting point.
• It doesn't conduct electricity because there are no free electrons.

Graphite:

• In graphite, each carbon atom forms 3 covalent bonds which creates sheets of carbon atoms arranged in hexagons.
• The covalent bonds are held together weakly, so they're free to move over each other. This makes graphite soft and slippery.
• Graphite has a high melting point- the covalent bonds need a lot of energy to break.
• Each carbon atom has one delocalised electron which can move freely, so graphite conducts electricity and thermal energy.

Metallic bonding involves delocalised electrons:

• The electrons in the outer shell of metal atoms are delocalised and there are strong forces of electrostatic attraction between the poitive metal ions and the shared negative electrons.
• Metallic bonding is very strong and these substances include metallic elements and alloys.

Most metals are solid at room temperature:

• The electrostatic forces are very strong between the metal atoms and delocalised electrons, therefore most metallic compounds have very high melting and boiling points, so they're mainly solid at room temperature.

Metals are good conductors of electricity and heat:

• The delocalised electrons carry electrical current and thermal energy throughout the structure, so metals are good electricity and heat conductors.

Most metals are malleable:

• Most metals can be bent or hammered or rolled into flat sheets