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460 BCE
Democritus
born around 460 BC and died around 370 BC. Created the theory that everything is composed of atoms. Atoms are physically but not geometrically, indivisible, that between atoms there lies an empty space and atoms are also indestructible. -
John Dalton
Discovered the atom in 1808 based his theory off of the law of conservation of mass and the law of constant composition. -
Dimitri Mendeleev
Discovered the atom on 17 February 1869, he jotted down the symbols of the chemical elements putting them in order by their atomic weight. Which created the Periodic Table -
Eugene Goldstein
Discovered anode rays. He concluded that in addition to the electrons or cathode rays, that travel from negatively charged cathodes towards positively charged cathodes. -
JJ Thompson
In 1897 discovered the electron which lead to him proposing the model of the structure of an atom. -
Max Planck
German physicist who discovered the quantum of action, now referred as Planck’s constant h. His work laid the foundation for quantum theory -
Robert Millikan
Discovered electric charge using the oil drop experiment. He charged droplets of oil in between two electrodes. -
Ernest Rutherford
1911 he discovered the nuclear structure of the atom. His experiments showed when alpha particles are fired into gas atoms, a few are violently deflected. -
Niels Bohr
He proposed a theory for the hydrogen atom, which based on quantum theory that some physical quantities only take discrete values. (Nucleus) -
Werner Heisenberg
Discovered the uncertainty principle. Which states that a particles position and momentum cannot both be known exactly. -
Erwin Schrodinger
Austrian physicist formulated a wave equation that accurately calculated the energy levels of the electrons in atoms. -
James Chadwick
1932 He proved the existence of neutrons. Neutrons are elementary particles that devoid electronic charges