- In the middle of an atom Neutral atoms have no charge overall
- Contains protons and neutrons Charge on electrons is oppostie charge to protons
- Positive charge Number of electrons equals number of protons
The Electrons Molecules are groups of atoms
- Move around the nucleus Atoms can join together to create molecules
- Negatively charged Molecules can be made up by one or more elements
- No mass Held together by covalent bonds
- Tiny, but cover a lot of space
Halogens - Group 7
Chlorine 17 green gas The properties change as you go down the group
Bromine 36 red-brown liquid
Iodine 53 dark grey solid
The higher up the element is, the more reactive it will be as the shell with the missing electron is nearer to the nucleus, so the pull from the positive nucleus is greater.
You can use these trends to predict the properties of other haolgens e.g. fluorine
The elements in Group 7 take place in displacement reactions. This is where a more reactive element "pushes out" a less reactive element from a compound.
Chlorine & Iodine - Chlorine is more reactive. If you add chlorine water to potassium iodide solution they will react and create potassium chloride.
Iron corrodes easily. It rusts.
Rusting only happens when the iron is in contact with oxygen and water.
The chemical reaction that takes place is oxidation. The iron gains oxygen to form iron(III) oxide.
Water becomes loosely bonded to the Iron(III) oxide and the result is hydrated iron(III) oxide.
iron + oxygen + water -----> hydrated iron(III) oxide (rust)
To prevent rusting you can coat the iron with a barrier :
Painting/Coating with plastic - ideal for big and small structures.
Oiling/Greasing - has to be used when moving parts are involved, such as bike chains.
Zinc is often used as a sacrificial metal due to Zinc being more reactive than Iron.
A coating of Zinc can be sprayed onto the object, this is known as galvanising.