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460 BCE
Democritus
Democritus proposed that the world is made of empty space and tiny particles called atoms. He thought that atoms were the smallest particles of matter. He created the Atomic Theory. -
300 BCE
Aristotle
Aristotle believed that all matter was made of 4 elements which are fire, earth, air, and water -
Antoine Lavoisier
Lavoisier created the Law of Conservation. -
John Dalton
Dalton discovered that all matter is made of atoms. All atoms that make up the element have the same mass. -
Avogadro
Avogadro believed that equal volumes of different gases contain an equal number of molecules- Avogadro hypothesis -
Berzelius
He made a table of atomic weights which included 43 elements. -
Dmitri Mendeleev
Mendeleev created the Periodic Table of Elements -
J.J. Thomson
Thomson discovered the electron while experimenting with cathode-ray tube. He discovered that the model of the atom was spherical with electrons surrounding it. He made the Plum Pudding Model. -
Eugen Goldstein
Goldstein discovered the proton -
Erwin Schrodinger
Schrodinger suggested that the atom had an electron wave like an orbit- Electron Cloud Model. He also introduced wave mechanics. -
Henry Moseley
Moseley developed the X-ray spectra to study atomic structures. He found out that the atomic number of an element is equal to the number of protons in the nucleus. -
Sir James Chadwick
Chadwick discovered the neutron. -
Henri Becquerel
Becquerel discovered radioactivity. -
Curie
Curie discovered radium and polonium and coined term radioactivity -
Planck
Planck is credited for describing hot glowing matter using quanta. Created the Quantum Theory. -
Ernest Rutherford
Rutherford conducted the Gold Foil experiment which proved the existence of a nucleus, the Rutherford Model. -
Niels Bohr
Bohr created the Bohr Planetary Model which was inspired by the fact that gravity pulls things together. He developed a way to explain atomic structure using the Periodic Table of Elements. -
Robert A. Millikan
Millikan proved Albert Einstein's law describing photoelectric phenomenon. He discovered the charge of a electron. -
Quantum Mechanical Model
The Quantum Mechanical Model is the most recent model we hold as standard today -
Werner Heisenburg
Heisenburg proposed the principle of Indeterminacy. It means that you can't know the position and velocity of a particle. -
Lise Meitner
Meitner helped discover nuclear fission.
