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400
Democritus
Democitus thought that matter was made up of really small particles that couldn't be divided. He thought there were atoms with specific qualities. Like the atoms in liquids are smooth and round, but the atoms in solids are rough and prickly. Democritus did something like cutting an object into smaller and smaller pieces to prove that all matter is made up of small particles that can't be divided. -
450
Aristotloe
Aristotle thought that all substances were made up of four elements; earth, air, fire, and water. The elements were a combination of four qualities; hot, cold, dry, and wet. Fire was a combination of dry and hot, and water was a combination of cold and wet. With his theory, by the 1800s, scientists had enough data from his experiments to back up the atomic model of matter. -
Isaac Newton
Newton thought that atoms were held together with attractions know as forces. He also thought that matter is formed of "solid, massy impenetrable particles." -
John Dalton
Just like Democritus, Dalton thought that all matter was made up of individual particles, atoms that can't be divided. Dalton got his evidence of atoms by measuring the masses of elements that combine when compounds form. Dalton thought of an atom as a little, indestuctible particles with no inside organization. -
Hantaro Nagaoka
Hantaro based his model on the rings of Saturn. Meaning, the atom had a very massive nucleus, meaning it was a big planet, and electrons were moving around the nucleus, like the rings around Saturn. HIs experiment was the Saturnian model and his work on spectroscopy. -
J.J. Thompson
Thompson found that an atom is neutral; it has no positive or negative charge. J.J. Thompson used a device that in the center had a sealed glass tube, most of the air had been removed, and it had a metal disk at each end of the tube. wires had been connected to the metal disks as a source of electricity. When he turned on the current, one of the disks became negativly charged and the other became poslitivly charged, it would then start to glow. -
Ernest Rutherford
Ernest Rutherford was a chemist and physicist who developed the nuclear physics atomic model. He discovered the concept of the radioactive half life and that has contributed to our understanding of the atom. His experiment was discovering the concept of the radioactive half life. Rutherford was the first to ever split an atom. -
James Chadwick
Chadwick discovered the neutron, named because of its lack of electrical charge, which was previously an unknown particle in the nucleus of an atom. Chadwick discovered the neutron. Was named after its lack of electrical charge. -
Erwin Schodinger
His equation was based on the Heisenberg. For his experiment he combined equations from the behavior of waves with de Broglie's equation to make a better model. -
Henry Moseley
Moseley came up with the development of X-ray spectra so he could study atomic structure. (an X-ray spectra is a photograph taken with x-rays.) His experiment was: measuring the wave lengths of the x-rays given off by certain metals, was able to determine the number of positive charges in the nucleus of an atom, it was the first understanding of the atomic number. -
Ernest Marsden
Ernest Marsden was Rutherfords student and helped develop the alpha and beta radiation. He also helped Rutherford with his theory of the atom and spliting the atom. -
Niels Bohr
He expanded on Rutherford's earlier theory, Bohr published his theory which suggested that electrons travel in specific orbits around the nucleus, that outer orbits can hold more elctrons than the inner orbits and that these orbits determine the chemical properties of the atom. -
Louis de Broglie
