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460 BCE
Democritus
Brought uptime idea of an atom -
428 BCE
Plato
Plato theorized that these solid forms of matter are composed of indivisible elements shaped like triangles (contrary to the conception of atoms as spheres in Ancient Greece) -
Period: to
The Alchemists
The alchemists believed that all metals could turn into another by putting it at different pressures. Even gold! -
Robert Boyle
Demonstrated that matter is made of tiny particles that he called corpuscles (aka atoms) -
Antone Lavoisier
Defined the law of conservation of mass -
Billiard Ball Model
Proposed there model of an atom -
John Dalton
Best known for proposing the atomic theory
-Elements are made of extremely small particles called atoms.
-Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.
-Atoms cannot be subdivided, created, or destroyed.
-Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
In chemical reactions, atoms are combined, separated, or rearranged. -
Amedeo Avogadro
Advanced two hypotheses: (1) that equal volumes of gas contain equal numbers of molecules and (2) that elementary gases such as hydrogen, nitrogen, and oxygen were composed of two atoms. -
Dimitri Mendeleev
Mendeleev created the periodic table of elements and predicted other elements -
JJ Tompson
Discovered the electron -
Perrie and Marie Curie
Discovered strong radioactive elements in polonium -
Solar System Model
It speculated that atoms could look like the solar system -
Plum Pudding Model
Showed that there was a source of positive charge within the atom -
Albert Einstein
Einstein mathematically proved the existence of atoms -
Robert Millikan
An early accurate demonstration of the charge carried by an electron -
Ernest Rutherford
Demonstrated the nuclear nature of an atom -
Neils Bohr
Atomic physicist that introduced the Bohr model of an atom.
The model depicted the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus -
Henry G. J. Moseley
Concluded that the atomic number is the number of positive charges in the atomic nucleus -
Wener Heisenberg
Heisenberg formulated a type of quantum mechanics based on matrices -
Electron Cloud Model
Helped physicists build a model on an atom -
Erwin Schrödinger
He combined the equations for the behavior of waves with the de Broglie equation to generate a mathematical model for the distribution of electrons in an atom. -
James Chadwick
Discovered the neutron