C2 Elements, mixtures and compounds

Ionic bonding occurs when atoms lose or gain electrons to form a full outer shell

Groups 1,2 and 6,7 are most likely to undergo ionic bonding as it is easier for them to gain a full outer shell

As you go down group 1 and 2 reactivity increases because as the electron is further away from the nucleus, it is easier to lose electrons

As you go down group 6 and 7 reactivity decreases as it is harder for the nucleus to attract

Ionic compounds have a regular lattice structure that is tightly packed

They have strong electrostatic forces of attraction in all directions so:

There are high melting and boiling points

They don't conduct when solid as the ions are fixed, but when it melts it does

They can easily dissolve in water and carry a charge

This occurs between non-metals as they share electrons to gain a full outer shell

This creates a strong covalent bond because there is a strong electrostatic attraction between the positive and negative nuclei

These are small molecules created by strong covalent bonds

The intermolecular forces are very weak so :

They have low melting and boiling points as the particles can be easily parted

They don't conduct electricity as the atoms can't move

Most of the substances are gases or liquid at room temperature

They contain many strong covalent bonds

The structure is similar to giant ionic lattices, but there are no charged ions

They have high melting and boiling points but don't conduct electricity

Carbon forms many giant covalent structures because it can form up to four bonds

Pure diamond is lustrous and colourless

4 carbon bonds form to give a strong and rigid structure

Because of the strong covalent bonds, there is a high melting and boiling point :

This makes it ideal for use in cutting tools

Diamond does not conduct electricity because there are no free electrons or ions

Graphite is black and opaque 

Each carbon atoms form 3 covalent bonds in sheets

These sheets of carbon can slide over each other - which makes it good as a lubricating material

Graphite also has a high melting and boiling point and it conducts electricity due to the delocalised electrons

Graphene is a single sheet of graphite, Graphene is very strong and light and is better at conducting electricity because the delocalised electrons are completely free

Fullerenes are also made of carbon and are shaped as hollow tubes or balls

Different fullerenes contain different numbers of carbon

Like graphite, the fullerenes are arranged in rings and also have delocalised electrons to conduct electricity

They have pretty high melting and boiling points but are not as high as diamond or graphite

Nanoparticles are about 1-100nanometres across - fullerenes are nanoparticles

Nanoparticles have different properties from the bulk material

They also have a high surface area to volume ratio which gives them different properties to larger particles

Uses:
Because of the high SA:V ratio they make good catalysts

In cosmetics, they are used as they don't leave white marks on the skin

They can be used to reduce friction

Also, they can be used in sports equipment to make the plastic stronger and more durable without adding as much mass

Polymers are long chains of monomers

These are created using polymerisation - this normally needs a high temperature and a catalyst

Strong covalent bonds hold the atoms in the chains

If the plastic is made from weak intermolecular forces then the chains can slide over each other -this will cause a low melting point - LDPE

If the plastic has stronger bonds there is a higher melting point and it is more rigid - HDPE

Metals are in a strong regular structure with delocalised electrons

Strong metallic bonds are between delocalised electrons and positive ions

This causes a high melting and boiling point

They are also:

Malleable, strong, good conductors, and hard to break

They react with oxygen to form metal oxides and can be used in alloys for strong alloys

In chemistry, a substance is pure if it only contains a single element or compound

If it has more than one compound or element it is a mixture

To test for purity you can measure the boiling point and compare it to the expected result

If it is impure the boiling point will be higher or lower than the expected result

Simple distillation is used to separate out a liquid from a solution

You must use solutions with very different boiling points otherwise you need fractional distillation

Fractional distillation separates out a mixture of liquids due to their boiling point

The different liquids are then condensed and collected

Filtration is used to separate an insoluble solid from a liquid

The liquid runs through the filter paper but the solid is left behind

Crystallisation separate a soluble solid from a solution

You place the solution in an evaporating dish and heat it until crystals form

You then leave it to cool and filter the crystals

Mobile - where molecules can move, liquid or gas

Stationary - where molecules can't move, solid