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400
Democritus
In 400 BC Democritus founded the ancient atomist theory. He did no experiments. His model of the atom depended on analogies -
Period: 400 to
Atomic Theory Timeline
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Antoine Lavoisier
Father of modern chemistry. Named oxygen, hydrogen, and silicon, first to state law of conservation of mass. -
John Dalton
A chemist, meterologist and physicist pioneered the modern atomic theory and research in Colour blindness -
Law of Conservation of Mass
States mass is neither created nor destroyed. And matter remains constant over time. -
Dalton's Atomic Theory
Created a scientific theory based off of Democritus atom idea that all elements are created from indestructable particles called atoms. His theory introduced compounds also, when different elements are joined chemical reactions occur. -
Dmitry Mendeleev
Created Periodic Table of Elements and extended it throughout time. -
J.J Thomson
Discovered electrons by showing that cathode-rays could be deflected electrically. Also discovered Isotopes -
Robert Millikan
Made the plum pudding model and stated that the charge of an electron is negative. -
Ernest Rutherford
Discovered Protons. Concluded that the nucleus is made of protons. -
Niels Bohr
Developed model of Atom with nucleus in center and electrons orbiting it. Won Nobel Prize in Physics. -
Erwin Schrodinger
Developed results in the Quantum Theory which formed basis of wave mechanics. -
Henry Moseley
Sorted elements in periodic table which is still accepted today. Also adavanced the concept of the atomic number. -
James Chadwick
Discovered the neutron and that it has no charge and is in the nucleus. -
Plum Pudding Model
His discoveries used the falling drop method which balanced downward gravational pull with buoyant and electrical qpward forces between electrons. -
Gold Foil Experiment
Showed atom was made up of empty space with electrons flowing and a positive charged nucleus in the middle. -
Rutherford Model
Model that proved the plum pudding model wrong and the model contained a nucleus. -
Bohr Plantary Model
Depicts the atom as a small positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus. -
Rutherford Model
Showed that the atom was made of empty space were electrons moved with a nucleus in the center with postive particles. And that the electrons orbit the nucleus. -
Electon Cloud Model
An atom model where electrons are no longer depicted as particles moving around the nucleus in a fixed orbit and showed exactly were the paricles are. -
Quantum Mechanical Model
Showed behavior of particles in the atomic realms and diagramed the electron clouds.
