Electricity in Chemistry

1. 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.

2. 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.

3. 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.

4. 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+

5. 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-

6. 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.

7. Electrolysis • 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.

8. 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 Cl2 gas.

9. Structure of Covalent Compounds • Covalent compounds are either – molecules of Networks. • Molecules– A small group of atoms held by a covalent bond. E.g. Co2, C2H4. • 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. SiO2 ( sand)

10. 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.

11. Ionic formula • This is the chemical formula – but also showing the charge of the ions. • StepsExample • Symbol Na O • Valency at top Na1 O2 • Cross Over Na2O1 • Put in charge (Na+)2 O 2-

12. 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-