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427 BCE
Plato
Plato theorized that the solid forms of matter are composed of indivisible elements shaped like triangles. -
400 BCE
Democritus
Democritus theorized that atoms were specific to the material which they composed. -
Robert Boyle
Boyle discovered the volume of a gas is inversely proportional to its pressure. If the pressure goes up, then the volume goes down. -
The Alchemists
The Alchemists believed that all metals were formed from two principles mercury and sulfur. -
Antone Lavoisier
Lavoisier defined the law of conservation of mass and discovered mass is neither created nor destroyed in chemical reactions -
Billiard Ball Model
Created in the early 1800's by John Dalton. Shows the shape of an atom. -
John Dalton
Dalton's theory suggested that all matter was comprised of indivisible and indestructible atoms with distinct masses and properties. -
Amadeo Avogadro
Avogrado discovered that equal volumes of gas contain an equal number of molecules. -
Dmitri Mendeleev
Mendeleev invented the periodic table. -
JJ Thompson
Thompson discovered the electron. -
Pierre and Marie
Pierre and Marie discovered radioactive elements such as polonium and radium. -
The Plum Pudding Model
Created by Thomas Thompson in 1904. Shows the positive and negative charges in an atom. -
Albert Einstein
Einstein mathematically proved the existence of atoms. -
Robert Millikan
Millikan found the accurate determination of the charge carried by an electron. -
Ernest Rutherford
Rutherford established that the mass of the atom is concentrated in its nucleus. -
Henry G.J. Mosely
Mosely discovered the number of positive charges in the nucleus of an atom- the atomic number. -
The Solar System Model
Created by Neils Bohr in 1913. Shows the nucleus compromised of positive and neutral charges surrounded by negative charges. -
Neils Bohr
Bohr proposed a model of the atom in which the electron was able to occupy only certain orbits around the nucleus. -
Electron Cloud Model
Created in 1926 by Erin Schrödinger and Werner Heisenburg. Shows nucleus surrounded by a cloud of negative charges- the electrons. -
James Chadwich
Chadwich discovered the neutron.