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Democritus's Atomic Theory
442 BC
Democritus claimed the theory of atoms and void; the universe is made up of empty space and a nearly infinite number or invisible particles differing in arrangement, form, and position. He stated that all matter is composed of indivisible atoms. -
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Aristotle
384-322 BC
Aristotle developed methods for the gathering of scientific fact. His work provided the basis for scientific work more than a millenium. -
Lavoisier
A French chemist that proved the conversation of matter and explained the mysteries of fire. -
John Dalton
An English chemist who proposed the Atomic Theory which stated that all matter was composed of small indivisible particles called atoms.These atoms possess unique characteristics and weight for different elements. He also stated that three types of atoms exist: simple, compound and complex. -
Crookes
Developed the Crookes tube and in it produced cathode rays for the first time. -
J.J. Thomson
First to measure the electron. Developed the plum-pudding model of the atom. Described the atom as a slightly positive sphere with small electrons inside. -
Ernest Rutherford
Inferred a small, dense, positively-charged nucleus as the result of the alpha particle scattering gold foil experiment. -
Hantaro Nagaoka
Proposed an atomic model called the Saturnian Model to desribe the structure of an atom. -
Robert Millikan
Discovered the charge of an electron with his oil drop experiment. -
Neils Bohr
Proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit. -
Louis de Broglie
Discovered that electrons have a wave/ particle duality. -
Edwin Schrodinger
Schrodinger furthered Bohr's model and stated that rather than electrons being distributed within an electron configuration of shells and energy levels, they are arranged in orbitals within electron clouds. -
James Chadwick
Discovered the existence of neutrons, the particle without any electrical charge and a fundamental building block of the atom's nucleus.
