Nature of science:

Theories can be supported, falsified or replaced by new theories—acid–base theories can be extended to a wider field of applications by considering lone pairs of electrons. Lewis theory doesn't falsify Brønsted–Lowry but extends it. (2.5)

• A Lewis acid is a lone pair acceptor and a Lewis base is a lone pair donor.
• When a Lewis base reacts with a Lewis acid a coordinate bond is formed.
• A nucleophile is a Lewis base and an electrophile is a Lewis acid

Applications and skills:

• Application of Lewis’ acid–base theory to inorganic and organic chemistry to identify the role of the reacting species.

Guidance:

• Both organic and inorganic examples should be studied.
• Relations between Brønsted–Lowry and Lewis acids and bases should be discussed.

• Acid–base theory has developed from the ideas of people from different parts of the world through both collaboration and competition.

Theory of knowledge:

• The same phenomenon can sometimes be explored from different perspectives, and explained by different theories. For example, do we judge competing theories by their universality, simplicity or elegance?

Utilization:

• Syllabus and cross-curricular links:
• Topics 4.2 and 4.3—covalent molecules and Lewis dot diagrams
• Topic 13.2—transition metal complexes
• Topic 20.1—nucleophiles

Aims:

• Aim 6: Transition metal complexes could be experimentally explored.
• Aim 7: Animations can be used to distinguish between the different acid–base theories.