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460
Democritus
Matter could not be divided into smaller pieces forever, eventually the smallest possible piece would be obtain. The piece would be indivisible. He named the smaller piece of matter "atomos", meaning not to be cut. -
Period: 460 to
Atomic theory
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Antione Lavoisier
Father of Modern Chemistry. Discovered the Law of Conservation of Mass. Said that an element as a simple substance that could not be broken down by any known method of chemical analysis. -
John Dalton
Discovered that all matter is made of atoms . Atoms are indivisible and indestructable. All atoms of a given element are identical in mass and properties. Dalton Atomic Theory -
J.J. Thomson
Credited on discovering electrons and isotopes. Was awarded nobel prize in 1906. Invented the mass spectrometer. Did the Cathode Ray Tube experiment. Made the Plum Pudding Atomic Model. -
Robert Millikan
Measured the charge of an electron with the oil drop experiment allowing for the calculation of the mass of the electron and the positively charged atoms. -
Dimitri Mendeleev
Created the periodic table. Saw that when elements are arranged in order of increasing atomic mass, there were similarities in their chemical properties. -
Ernest Rutherford
planetary model, electrons orbit the nucleus like planets around the sun. He conducted an experiment with two other scientists, in which they studied the deflection angles of "alpha particles" that they shot through a microscopically thin layer of gold(gold foil experiment). -
Erwin Schrodinger
Took Bhors model and used mathematics to find where exactly electrons are. Introduced the concepts of sub-energy levels. Made the electron cloud model. -
Henry Moseley
Made the periodic table more accurate by positioning by atomic number. Developed the application of x-ray spectra to study atomic structure. -
James Chadwick
Proved the existence of the nuetron in 1932. Studied under Ernest Rutherford. -
Niels Bhor
Discovered that electrons are arranged in concientric circular orbits around the nucleus. Stationary orbits, Bhor model, Bhor planetary model.
