4. Types and hexagons

‘Types and hexagons’ introduces some of the key characters involved in making important contributions to the field of chemistry: Antoine Fourcroy, who created the divisions of inorganic and organic chemistry; Friedrich Kekulé, who defined organic chemistry as the chemistry of carbon compounds and proposed benzene’s hexagonal structure; Justus Liebig, who applied chemistry to agriculture, physiology, medicine, nutrition, and industry; Berzelius, who introduced the term isomerism and the electrochemical system of classification; French chemists Charles Gerhardt and August Laurent; Edward Frankland, who proposed valency; Alfred Werner and his coordination theory of molecular structure; and Alexander Williamson, who had a pivotal role in the development of 19th-century chemistry.