Chemistry Topic 2

What are ions?

They are charged paticles - they can only be a single atom or gorups of atoms

What happens when metals form ions?

They loose electrons from their outer shells giving them a positive charge

What happens when non-metals form ions?

They gain electrons into their outer shell meaning they get a negative charge

Which groups are most likely to form ions and why?

Groups 1,2,6 and 7 are most likely to fomr ions because - groups 1 and 2 are metals and loose electrons to form positive ions - groups 6 and 7 are non-metals they gain electrons to form negative ions

Whats happens during ionic bonding?

The metal atom looses electrons to form a positively charged ion and the non metal gains electrons to form a negatively charged ion.

What are ionic compounds?

They have a structure called a giant ionic lattice. The ions are closely packed regular lattice arrangement and there are very strong electrostatic forces of attraction between oppositely charged ions in all directions in the lattice

What is the formula for ionic compounds?

The empiricial formula — it tells you the simplest ratio of ions in the lattice. To find the empiricial formula of an ionic compound from a diagram of its structure, count the number of each ions in the diagram then cancel them down to the lowest whole number ratio of ions.

What similar properties do all ionic compounds have?

They all have high melting points, and high boiling points

What are covalent bonds?

When non-metals and non-metals shair pairs of electrons to make a covalent bond.

The positevly charged nuclei of the bonded atoms are attracted to shared pair of electrons by electrostatic forces, making covalent bonds very strong

What are simple molecular structure?

they are made up of molecules containing a few atoms joined together by covalent bonds.

What are the propeties of simlpe molecular substances?

The atoms within the molecules are held together by very strong covalent bonds. By contrast the forces of attraction between these molecules are very weak

The substances are either gases or liquids at room temp

Very low melting and boiling points

The molecules get bigger as the intermoleculer forces get stronger ao more energy is needed to break them so the melting and boiling points increase

They dont conduct electricity as they arent charged and have no free electrons

What are polymers?

They are long chains of repeating units. In a polymer lots of small units are linked together to form a long molecule that has repearing sectiosn

How are polymers joined togther?

All the atoms in a polymer are joined by strong covalent bonds

How large are the are the covalent bonds in polymers?

They are larger than the bonds between simple covalent molecules so more energy is needed to break them. This means most polymers are solid at room tempreture. The intermolecular forces are atill weaker than ionic or covalent bonds, so they generally have lower boiling points than ionic or giant covalent compounds.

How do you find the molecular formula of a polymer?

write down the molecular formula of the repeating unit in brackets and put an n outside

What are giant covalent structures?

They are macromolecules, and in them all of the atoms are bonded together by strong covalent bonds.

What are the properties of giant covalent structures?

They have very high melting and boiling points as lots of energy is required to break the covalent bonds between the atoms

Why can they not conduct electricity?

They cant as they dont contain any charged particles so dont conduct electricity not even when molten

What are the properties of diamond?

It is made up of carbon atoms that each form four covalent bonds this makes diamond really hard

The strong covalent bonds take a lot of energy to break and give diamond a very high melting point

It doesn conduct electricity because it has no free electrons

What are the properties of graphite?

In graphite each carbond atom only forms three covalent bonds creating sheets of carbon atoms arranged in hexagons

There arent any covalent bonds between layers - theyre only held together weakly, so theyre free to move over eachother. This makes graphite soft and slippery, so its ideak as a lubricating metal

Graphites got a high melting point - covalent bonds in the layers need loads of energy to break

Only three out of each carbons four outer electrons are used in bonds, so each carbon atom has one electron that are delocalised and can move so graphite conducts electricity and thermal energy

What is graphene?

Graphene is a sheet of carbon atoms are joined togther in hexagons. The sheet is just one atom thick making it two-dimentional substance

The network of covalent bonds makes it very strong. Its also incredibly light, so can be added to composite materials to improve their strength without adding much weight

Like graphite it cintains delocalised electrons so can conduct electricity through the whole structure. This means it has the potential to be used in electrons

What are fullerenes?

They are molecules of carbon shaped like closed tubes or hollow balls

What are the properties of fullerenes?

They are mainly made up of carbon atoms arranged in hexagons. But they can also contain pentagons or heptagons

They can be used to cage other molecules. The fulleren structure forms around another atom or molecule, which is then trapped inside. This could be used to deliver a drug into the body

Fullerenes have a huge surface area so they could help make great industrial catalyst - individual catalyst molecules could be attached to the fullerenes. Fullerenes also make great lubricants