2. Electricity in Chemistry An electric current is a flow of charge – this can be either electrons or charged particles called “ions” A conductor is a substance that lets electricity through. Metal elements and Graphite(Carbon) are good conductors. An insulator is a substance that does not let electricity through it. Non-metals elements are good insulators.

3. Testing Conductivity We can test whether a substance conducts using simple apparatus: A bulb, a battery, conducting wires and the test substance. We place the test substance in the circuit – to complete it – if the bulb lights - it is a conductor! If the bulb does not light – it is an electrical Insulator.

4. Other conductors Covalent compounds – (non- metals joined)– do not conduct electricity. Compounds that are made of metals and non-metals joined, IONIC COMPOUNDS, will conduct electricity, when in solution or molten. This is because the charged particles, ions, which they are made up of, can move.

5. Forming Positive Ions Ions are charged particles. When a metal atom looses electrons they form positively charged ions. The number of electrons they loose depends on the valency of the group they are in. Example Lithium is in group 1 – valency 1 – it looses 1 electron forming a Li + ion Magnesium – group 2 – valency2 – looses 2 electrons to form Mg 2+

6. Forming Negative Ions Non metals gain electrons to form negative ions. Valency determines how many electrons they gain Example Br is in group 7 – valency1 – it gains 1 electron forming Br – Oxygen is in group6 – valency 2 – it gains 2 electrons forming O 2-

7. The Ionic Bond An Ionic Bond is formed when positive metal ions are attracted to negative non-metal ions – electrostatic attraction. It is a very strong bond. An ionic compound is made from a large network of positive and negative ions held together. They form a “ CRYSTAL LATTICE” Ionic compounds have high Melting and Boiling Points – they are usually solids at room temperature.

8. Electrolysis is the process where a compound is split up using electricity. An “electrolyte” is the compound that is split. The “electrolyte” - which must be molten, or in solution, is placed in a conducting cell. The + and – electrode are placed in the solution and a DC current supply is switched on.

9. Electrolysis of Copper chloride During electrolysis the Cu 2+ moves to the – Electrode where it gains electrode where it gains 2 electrons forming atoms. We can see a brown solid forming – Copper. The Cl - ions move to + electrode, loose electrons forming atoms. We cans see bubbles and smell Cl 2 gas.

10. Structure of Covalent Compounds Covalent compounds are either – molecules of Networks. Molecules – A small group of atoms held by a covalent bond. E.g. Co 2, C 2 H 4. They have low MP’s and BP’s. Usually gases and liquids. Covalent Networks – thousands of atoms held by covalent bond. Usually solids. Have High MP’s and BP’s e.g. SiO 2 ( sand)

11. Ion migration We can monitor the movement of certain ions because they are coloured. Copper – blue, Cobalt – pink, Nickel – green, Permanganate – purple, Chromate – yellow, Dichromate- orange. These are transition metals. The colour of the compound is a mixture of the colour of the ions which make it up.

12. Ionic formula This is the chemical formula – but also showing the charge of the ions. StepsExample SymbolNa O Valency at topNa 1 O 2 Cross OverNa 2 O 1 Put in charge(Na +) 2 O 2-

13. Ion electron Equations Forming metal ions Metal atom on LHS then an arrow followed by the formula of the ion and how many electrons they have lost. E.g. Mg—>Mg 2+ + 2e Non Metal ions Atom on LHS plus electrons gained – arrow then ion on RHS E.g. S + 2e —> S 2-