History of Elements

1. History of Elements Science Myette

2. 450 BC – Empedocles suggested the four elements: earth, air, water and fire

3. 400BC – Democritus proposed that matter was made of tiny particles that could not be seen; named them atoms. His idea was not acknowledged for another 2000 years. Democritus’ ideas opposed by Aristotle who still believed in the ‘four elements’.

4. Going for Gold? • 1669 – Hennig Brandt (Hamburg alchemist) discovered phophorus by distilling urine but didn’t know he had while attempting to make gold. • Robert Boyle – English scientist (1627-1691) believed air was a mixture and not an element, opposed the ‘four element theory’, and was convinced Brandt had found an element. Published a book called the ‘Skeptical Chemist’ coining the present definition of elements as ‘pure substances that cannot be chemically broken down into simpler substances’.

5. The Scientific Revolution • 1700’s – Scientific Revolution where Henry Cavendish, Joseph Priestley and Antoine Lavoisier discovered elements ‘by accident’. Cavendish mixed a metal with an acid, producing a flammable gas; hydrogen. Priestley made oxygen by focusing sunlight on a compound mercury II oxide, producing mercury and oxygen. Antoine Lavoisier recognized, from the work of the previous two scientists, that they had isolated elements. He suggested air was a mixture of elements. Cavendish heard this, and heard of Priestly’s gas, combined it with his own gas, and produced water, proving water wasn’t an element. Cavendish published his results, and continued his research, while Lavoisier, hearing of Cavendish’ discovery, began to understand what an element was. He continued discovering, along with his wife, a number of additional elements and published his findings, naming the elements and excluding both Cavendish and Priestley from his work.

6. Henry Cavendish (1731-1810) • Isolated hydrogen • Made water from hydrogen and oxygen and published his results.

7. Joseph Priestly • Isolated oxygen by heating mercury II oxide

8. Antoine Lavoisier • Discovered many elements with his wife, Marie Lavoisier • Named the gases he discovered, excluding the work of Priestley and Cavendish • In 1781, explained the difference between elements and ‘non-elements’.

9. The Atom • In 1808, English Chemist John Dalton published a theory explaining the difference between elements and non-elements, called the ATOMIC THEORY. The atomic theory stated: • All matter is made of atoms which particles are too small to be seen • Each element has its own type of atom • Compounds are created when atoms of different elements link together. In a compound, all compound atoms are alike. • Atoms cannot be created or destroyed (page 168 in your text!)