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Period: 500 BCE to
The Alchemists
The alchemists’ theory stated that all metals are composed of mercury and sulfur and that it is possible to change base metals to gold.The alchemists’ contribution to atoms are what make up the foundation of the periodic table of elements today. -
450 BCE
The Classical Elements
The four elements - fire,water,air and earth, discovered by Aristotle in 450 BC, known to be the smallest devisions anything cold be sorted into. -
Joseph Proust
Joseph Proust published his Law of Definite Proportions, which states that a compound is composed of exact proportions of elements by mass regardless of how the compound was created. -
Antoine Lavoisier
The first to come up with a defiition of elements as 'indevisable particles which we have found no means of separating', and alos the first to recognise a compound in chemistry. -
John Dalton
John Dalton's atomic theory states that :
All matter is made up of atoms. Atoms are indivisible and indestructible.
All atoms of a given element are identical in mass and properties.
Compounds are formed by a combination of two or more different types of atoms.
A chemical reaction is a rearrangement of atoms.
These four points make up the foundation of chemistry. -
JJ Thomson
JJ Thomson, a famous physicist whose research led to the discovery of ‘corpuscles’, now known as electrons. Thomson was adamant that all matter was made up of tiny particles that are much smaller than the atoms. -
Ernest Rutherford
Ernest Rutherford came up with an atomic model in which a positively charged core with a concentrated mass called the nucleus, would be surrounded by a negatively charged component called an electron which would circle it like planets revolving around the sun. -
James Chadwick
James Chadwick, an English physicist, was the first to publish the existence of a neutron in 1932, based off an experiment conducted by Frédéric and Irène Joliot-Curie, comming to a conclusion of the heavy particles with no charge (now known as neutrons).
