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Period: 550 BCE to
Atomic Model Timeline
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500 BCE
The Alchemists
The Alchemists developed the theory that all metals are made of mercury and sulfur, and that it is possible to change base metals into gold. -
440 BCE
Democritus
Democritus discovered the atom -
427 BCE
Plato
Plato discovered that atoms mathematically break down into geometric shapes. -
Robert Boyle
Boyle helped develop the definition of an element -
Antoine Lavoisier
Lavoisier came up with the law of conservation of mass which states that matter changes forms but cannot be created nor destroyed -
Billiard Ball Model
The billiard ball model of an atom was a model in which an atom is represented as a tiny indivisible spherical object that cannot be more simplified. -
John Dalton
Dalton's Atomic theory states that all matter is composed of atoms and that atoms of each element are the same mass and properties but differ from that of other elements. It also states that atoms cannot be subdivided nor destroyed. -
Amedeo Avogrado
Avogrado discovered that elements could exist as molecules which were comprised of multiple atoms joined together. -
Dimitri Mendeleev
Mendeleev created the periodic table -
Albert Einstein
Einstein is famous for the theory of Relativity in which special relativity applies to elementary particles (electrons) and their interactions -
JJ Thompson
Thompson discovered the electron. -
Pierre and Marie Curie
The Curies discovered polonium and radium which are radioactive elements. -
Plum Pudding Model
The plum pudding model of an atom is electrons surrounded by a volume of positive charge. -
Robert Millikan
Millikan discovered the value of the charge of an electron. -
Ernest Rutherford
Rutherford discovered the nucleus of an atom. -
Neils Bohr
Bohr proposed the theory for the hydrogen atom and discovered that electrons do not come into contact with the nucleus of an atom. He also created the solar system model of the atom. -
Solar System model
The solar system model of an atom is a model in which there are electron in orbit around a nucleus similar to the way planets orbit around the sun. -
Henery G. J. Moseley
Moseley discovered the atomic number of each element which led to the accurate organization of the periodic table. -
Werner Heisenberg
Heisenberg calculated the behavior of electrons which circle around the nucleus of an atom using the uncertainty principle. -
Erwin Schrodinger
Schrodinger created the equation that can pinpoint the placement of electrons. This made it possible to make very accurate models of atoms. -
Electron Cloud Model
The electron cloud model of an atom is a model in which the atom consists of a nucleus surrounded in a cloud of rapidly moving electrons. -
James Chadwick
Chadwich discovered neutrons.
