Topic 14 - Redox II

• Oxidation is the loss of electrons, and reduction is the gain of electrons. Oxidation causes the oxidation number to become more positive, whilst reduction results in the oxidation number becoming more negative.
• Blocks of the Periodic Table, such as the s-block and d-block, indicate the orbital of the outer electron.
• During reactions, s-block, d-block and some p-block species tend to undergo oxidation, whilst p-block elements (further to the right of the Periodic Table) tend to undergo reduction
• Electrochemical cells use redox reactions, since the electron transfer between products creates a flow of electrons. This flow is an electrical current that flows between electrodes in a cell.
• A potential difference is produced between the two electrodes in an electrochemical cell which can be measured using a voltmeter.
• Most electrochemical cells consist of two solutions, metal electrodes and a salt bridge.
• A salt bridge is a tube of unreactive ions that can move between the solutions to carry the flow of charge, whilst not interfering with the reaction.
• Each electrochemical cell contains two half-cells which make up the full chemical cell. These half-cells each have a cell potential which indicates how it will react (in either an oxidation or reduction reaction).
• If measured under standard conditions, cell potentials are measured compare to the standard hydrogen electrode (SHE) to give a numerical value for the half-cell potential.
• Standard hydrogen electrode (SHE) is used for reference on all half-cell potentials as it has a standard electrode potential of zero.