Atom = Smallest part of a molecule
Molecule = Atoms that have joined together
Element = One type of an Atom ONLY
Compound = Two or more different atoms chemically bonded together
Mixture = Two or more substances that are not chemically united and that exist in no fixed proportion to each other.
Electron Shell Rules and Atoms
Electron Shell Rules Electrons occupy energy levels (shells) The lowest energy level is always filled first
- 1st Shell - 2 Electrons
- 2nd Shell- 8 Electrons
- 3rd Shell - 8 Electrons and on and on.....
The First Shell is always only filled with two electrons but the rest of the shells are filled with eight.
- Atoms are happier when they have a full electron shell
- In most atoms their outer electronic shell is not full
- This Makes the atoms reactive
- Atoms are reactive they need to have a full outer shell to be stable they do this by loosing, gaining or sharing electrons.
Types of Bonding
Sharing electrons occurs between two non-metals: e.g CO2, H2O
Transference electrons this occurs between a metal and non-metal: e.g NaCl, MgO (usually group 1/2 metals and groups 6/7 non metals)
The arrangement of atoms in metals.
Convalent Bonds are formed when atoms share electrons, this happens between two non metals and each pair of electrons are shared in a single bond.
Drawing Convalent Bonds
Hydrogen H2 H - H
- An is a charged atom.
- Positive ions are formed when atoms loose electrons from their outer shell e.g Na+
- Negative ions are formed with atoms gain electrons from outer shell e.g Cl-
Making ionic compounds
The word equation for sodium with chlorine:
Sodium + Chlorine -> Sodium Chloride
2Na(s) + CL2(g) -> 2NaCl You have to make sure the equation is Balance!
(Gases travel in pairs expect Nobel Gases)
- Atoms are arranged in regular layers
- Positive ions in metals are held together by electrons from outer shell of each atoms
- The delocolised electrons are free to move throughout the metal
- Giant Lattice with metallic bonds
- Free Sea of outer electrons
Properties of Metals
- Metals are strong, malleable, Ductile, Have high melting and boiling points, good conductors of heat and electricity and conduct heat when solid and liquid.
Growing Crystals: - We used copper and silver nitrate which caused a displacement reaction. - Copper is more reactive than silver
Cu(s) + 2AgNO3(aq) -> 2Ag(s) + Cu(NO3)2(aq)
Properties of Ionic Compounds
Properties of Ionic Compounds
- Lattices are arrangement's of ions that a closely packed together. - The ions are closely packed together which means there ate very strong attractive forces - Between oppositely charged ions. - The have high melting and boiling points and are solid at room temperature
Lots of energy is needed to overcome the forces of attractions and break the lattice apart.
Ionic compounds conduct electricity: however
- Do not conduct when there in a solid
- They do When molten (melted)
- They dissolve to form solutions that conduct electricity
- Distilled water does not conduct electricity as there are no ions
- Tap water can conduct electricity as there are dissolved ions in it they are free to move.
Giant Convalent Structures
Giant Convalent Structures
Substances Melting Points Boiling points
Diamond 3350 4827 Graphite 3652 4200 Silicon Dioxide 1650 2230
The melting and boiling points are very high.
- Giant Convalent Structure = strong convalent Bonds
- Each Carbon atom is attached to four more carbon atoms (each carbon has four bonds)
- It is hard - the atoms cannot slide over each other
- The are chemically unreactiver
The Properties of Polymers
The properties of Polymers
Monomer - a small reactive molecules that react together repeating sequences to form a large molecule.
Polymer - a substance made from many repeating units joined together.
Thermosoftening Thermosoftening : melt when heated they are used to make bowls, buckets and cling film e.g polythene, polypropene
Thermosetting Plastics Thermosets: do not soften when heated they are used to make saucepan handles and electrical fittings.
Low Density Polythene; is made from ethene -
- They are really small particles compared to normal particles and typically the size of small molecules and far to small to see without a microscope
- They range from about 100m to 1m
- Working with nanoparticles is called nanotechnology
- Nanoparticles have a very large surface area compared with their volume
- So they are able to react quickly
Uses of nanoparticles
Nanoparticles of silver are often put in particles or non smelling socks it stops bacteria growing, we cant stop the chemicals but can stop the bacteria. the silver in the socks stop the fabric from smelling.
Nanoparticles can also be used in chemical testing they use one strip to hold different droplets of blood given doctors information quickly.
ionic bonding continued...
Opposites Attract - Lattices
The oppositely charged ions are attracted into a lattice that gets bigger and bigger until it consists of millions of ions
Metallic Bonding continued
Metallic Crystlas - Atoms that are arranged in regular layers, they are closely packed together and form a giant lattice.
When they form a lattice the outer electrons can share with each other.
Structure of Metals
- Positive Ions made in metals are held together by electrons from the outer shell. - These delocalised electrons are free to move throughout the metal.
ionic compounds continued
Remember they DON'T conduct as a solid only as a liquid, this is because the ions are free to move around.
IONs are charged atoms however they are atoms that have lost or gained electrons.
- if they loose electrons they become positive + e.g any metal
- if they gain electrons they become negative - e.g any non metal in group 6 or 7.
convalent structures continued
Graphite Contains layer of atoms that slide over each other - this makes graphite slippery Each Carbon only has three bonds - leads to delocalised electrons which conduct electricity.
Silicon Dioxide Similar structures to diamond Each Si has four bonds and Each O has two bonds They are Strong convalent bonds