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460 BCE
Democritus
He said that different atoms have different shapes and sizes. He also determined that atoms are solid, homogeneous, indestructible, and indivisible. -
384 BCE
Aristotle
He famously denied the existence of atoms, and this theory went undisputed for over 2,000 years. Instead, he thought that 4 elements made up all matter. -
John Dalton
Dalton is considered the father of modern atomic theory. He developed 5 basic laws: 1. matter is made up of atoms 2. atoms are indivisible and indestructible 3. atoms of the same element are identical, atoms of different elements are different 4. atoms come together in whole ratios to form compounds 5. in chemical reactions, atoms can be separated, combined, and rearranged. -
JJ Thomson
JJ developed the cathode-ray tube and said that cathode rays are composed of identical, negatively charged particles. He is also famous for developing the 'plum-pudding' atomic model. He discovered electrons and disproved the theory that atoms are indivisible. -
Robert Millikan
Millikan said that the mass of an electron must be very small for it to have such a large charge. He is also famous for his oil drop experiment which resulted in him finding the charge and mass of electrons. -
Ernest Rutherford
He is famous for discovering the nucleus, and developing the nuclear model of the atom. He is also well known for his gold foil experiment. He said that atoms are mostly empty space with a nucleus and free-floating electrons. -
Niels Bohr
Bohr is famous for developing the planetary model of the atom. He said that electrons orbit the nucleus just like planets orbit the sun. -
Schrodinger
He viewed electrons as being housed in clouds, and said that electrons behave like waves. He developed the quantum mechanical model of the atom. -
James Chadwick
Chadwick is famous for discovering neutrons.
