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330
Aristotle propses element theory
Aristotle proposes the four element theory: earth, air, fire & water -
400
Democritus proposes the atom
400 BC Democritus and Leucippus propose the idea of the atom, an indivisible particle that all matter is made of. -
First list of elements
Antoine Lavoisier wrote the first extensive list of elements containing 33 elements & distinguished between metals and non-metals -
First periodic table
Jakob Berzelius developed a table of atomic weights & introduced letters to symbolize elements -
Mendeleev's table
Dmitri Mendeleev produced a table based on atomic weights but arranged 'periodically' with elements with similar properties under each other. His Periodic Table included the 66 known elements organized by atomic weights. -
Radioactivity
Ernest Rutherford discovered the source of radioactivity as decaying atoms -
Periodic Law
Henry Moseley determined the atomic number of each of the elements and modified the 'Periodic Law'