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Democritus
Made the atomic theory. He said that everything was made up of small particles called atoms -
Dalton
Proposed the atomic theory. -
Newlands
his “law of octaves” noted a pattern in the atomic structure of elements with similar chemical properties and contributed in a significant way to the development of the periodic table. -
Crooke
discovered the element thallium and made special studies of radioactive substances in the course of which he invented the crookes tube, -
Mendeleev
His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties. -
JJ Thomson
Descovered the electron. To support this he made the "Plum Pudding" model -
Bohr
He suggested that the outer orbits could hold more electrons than the inner ones, and that these outer orbits determine the atom's chemical properties. -
Rutherford
discovered the existance of neutrons. His therory was that it had a reppeling effect to protons, keeping the nuclei together. He made an atomic model to support it -
Chadwick
Chadwick had created an experiment to answer the question of the unknown nucleus mass source, thus discovering the neutron. -
Arisotle
Aristotle said there were only four elements (earth, air, fire, water) and that these had some smallest unit that made up all matter. -
Period: to
Chemists contributions
