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500 BCE
The Alchemists
The Alchemists started testing Aristotle's theory of atomic shortly after Aristotle's death. Then, in 500 B.C., they discovered a substance that would transmute more common metals into silver and gold. -
428 BCE
Plato
Plato came up with the idea of Elements in 428 B.C. -
400 BCE
Democritus
in 400 B.C. Democritus created a theory that posited that matter is made up of small indestructible units called atoms. -
Robert Boyle
in 1640, Robert Boyle discussed the possibility of atoms existing, he proposed that the elements are composed of "corpuscles" of various sizes and types that can be able to organize themselves into groups that represent different chemical substances. -
Antone Lavoisier
In 1777, Antone Lavoisier was a French chemist who proved the conservation of matter and explained the mysteries of fire. In 1778, he named and recognized oxygen. -
John Dalton
John Dalton was an English chemist and teacher who used experimental evidence to form the Atomic Theory of Matter. In 1803 A.D. John Dalton proposed that compounds were atoms from different elements combined together and consisted of atoms that were identical and also had the same mass. He also came up with the Billiard Ball Model in 1803. -
Billiard Ball Model
John Dalton, in 1803, put forth the theory of the solid sphere or as it was also called, "Billiard Ball" model -
Amedeo Avogadro
Created the Avogadro's Hypothesis, which reasoned that simple gasses were not formed of solitary atoms but were instead compound molecules of 2 or more atoms in 1811 -
Dmitri Mendeleev
Dmitri Mendeleev created the periodic table in 1869. -
JJ Thompson
in 1897, JJ Thompson determined the charge to mass ratio of electrons. he also created the Plum Pudding Model in 1900. -
Pierre and Marie Curie
in 1898, Pierre and Marie Curie identified and studied radioactive elements -
Plum Pudding Model
JJ Thompson came up with the "Plum Pudding" theory thinking an atom had many positive and negative charges, in 1900 -
Albert Einstein
Albert Einstein proposed the quantum of light in which he stated that light is like a particle and also has a wave nature that is giving a dual nature. He also started the equivalence of energy and mass through the theory of special relativity. -
Robert Millikan
In 1908, Robert Millikan discovered the charge of an electron with his oil drop experiment -
Ernest Rutherford
Ernest Rutherford, in 1909, concluded a small, dense positively charged nucleus as a result of the alpha particles in a scattering gold foil experiment. Created the Solar System Model as well in 1900 -
Solar System Model
in 1911, Ernest Rutherford came up with the theory of the solar system and said an atom looked somewhat like it. He also discovered the nucleus of an atom. -
Neil Bohr
In 1913, Neils Bohr proposed an atomic structure theory that stated the outer orbit of an atom could hold more electrons than the inner orbit. -
Henry G.J. Mosely
In 1914, Mosely discovered that the number of protons in an element is its atomic number. -
Electron Cloud Model
one electron cloud model example was proposed by Erwin Schrodinger and Werner Heisenburg in 1926, though there were other models of the Electron Cloud Model, such as the one by Neils Bohr and the one by Ernest Rutherford. -
Werner Heisenburg
In 1926, Werner Heisenburg, along with Erwin Schrodinger, created the Electron Cloud model -
Erwin Schrodinger
in 1926, Erwin Schrodinger, along with Werner Heisenburg, created the Electron Cloud model. -
James Chadwich
in 1932, James Chadwich discovered that atoms consisted not only of protons and electrons but also neutrons.
