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400 BCE
Democritus
Greek Philosopher known for his concept of atoms, which was that everything was made up of tiny particles, which he called ‘atomos’ -
John Dalton
English chemist, physicist, and meteorologist known for his atomic theory. The main points of Dalton’s atomic theory are:
-All matter is made up of atoms
-All atoms of a given element are identical in size, mass and other properties, atoms of different elements differ in size, mass, etc.
-Atoms cannot be destroyed, divided, or created
-Atoms of different elements combine in ratios to form chemical compounds
-In chemical reactions, atoms are combined, separated or rearranged. -
J.J. Thomson
English physicist known for his discovery of the electron, he realized that the popular model of an atom did not account for negatively or positively charged particles -
Dmitri Mendeleev
Russian chemist and inventor known for arranging the sixty three elements based on atomic mass into a periodic table -
Eugen Goldstein
German physicist known for discovering canal rays or Kanalstrahlen, which helped him later discover protons -
Ernest Rutherford
British physicist known for discovering that atoms have a small charged nucleus surrounded by empty space, and are circled by tiny electrons -
Niels Bohr
Danish physicist that developed a model that depicts the atom as a small, nucleus surrounded by electrons that orbit around the nucleus -
Max Planck
German theoretical physicist that is best known as the creator of quantum theory, which helped with the understanding of atomic processes -
Robert Millikan
American experimental physicist whose oil drop experiment helped to measure the charge of an electron, which helped to understand the structure of the atom and atomic theory -
Werner Heisenberg
German theoretical physicist who is best known for his uncertainty principle and theory of quantum mechanics -
Erwin Schrodinger
Austrian physicist who developed the quantum mechanical model of the atom -
James Chadwick
British physicist who discovered the neutron in atoms
