• Oxidation and reduction can be considered in terms of oxygen gain/hydrogen loss, electron transfer or change in oxidation number.

• An oxidizing agent is reduced and a reducing agent is oxidized.

• Variable oxidation numbers exist for transition metals and for most main-group non-metals.

• The activity series ranks metals according to the ease with which they undergo oxidation.

• The Winkler Method can be used to measure biochemical oxygen demand (BOD), used as a measure of the degree of pollution in a water sample.

• Deduction of the oxidation states of an atom in an ion or a compound.

• Deduction of the name of a transition metal compound from a given formula, applying oxidation numbers represented by Roman numerals.

• Identification of the species oxidized and reduced and the oxidizing and reducing agents, in redox reactions.

• Deduction of redox reactions using half-equations in acidic or neutral solutions.

• Deduction of the feasibility of a redox reaction from the activity series or reaction data.

• Solution of a range of redox titration problems.

• Application of the Winkler Method to calculate BOD.

• Oxidation number and oxidation state are often used interchangeably, though IUPAC does formally distinguish between the two terms. Oxidation numbers are represented by Roman numerals according to IUPAC.

• Oxidation states should be represented with the sign given before the number, eg +2 not 2+.

• Titrations and using the Winkler Method to measure BOD.

• The oxidation state of hydrogen in metal hydrides (-1) and oxygen in peroxides (-1) should be covered.

• A simple activity series is given in the data booklet in section 25.