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Democritus BC
Democritus was a Greek philosopher. Unlike earlier theories, Democritus believed that fire, water, earth, and air were not the only elements. He thought that atoms were physically indivisible and everything was in the void, a vacuum with infinite space. He believed that the only things that existed were atoms and the void. The word atom is dervived from the Greek word atomos, which means indivisble. -
John Dalton
John Dalton was an English scientist who was born on September 6, 1766. Dalton's atomic theory had four parts. First, all matter is made of atoms. Atoms are indivisible and unable to be destroyed. All atoms of a element are the same in mass and other characteristics. Compounds are created by a combination of two or more different atoms. Lastly, a chemical change is a movement of atoms. -
J.J. Thomson
J.J. Thomson was an English scientist that was born on December 18, 1856. Thomson experimented with electricity currrents in empty glass tubes, or cathode rays. He thought that corpuscles were miniscule particles that made up atoms.Thomson made his suggestion after his discovery that Lenard rays could travel much further through air than expected for an atom-sized particle. He discovered the electron. -
Ernst Rutherford
Ernst Rutherford was a New Zealand born scientist who was born on August 30, 1871. In Rutherford's gold foil experiment, he aimed a beam of alpha particles at a piece of gold foil and expected them all to go through, but some bounced back. This proved that the center of the atom had a positive charge and had electrons around it, unlike Thomsons idea with the electrons in the center. -
Niels Bohr
Niels Bohr was a scientist from Denmark who was born on October 7, 1885. His atomic model had the protons and neutrons in the nucleus and electrons in orbit of the nucleus. It is important because it describes most atomic features without high-level mathematics. -
Erwin Schrodinger
Erwin Schrodinger was an Austrian scientist who was born on August 12, 1887. Moving electrons can follow wave directions, allowing for the prediction of the location of the electrons. -
James Chadwick
James Chadwick was an English scientist who was born on October 20, 1891. He proved the neutron existed by doing experiments with tracking particle radiation. Experiments like these had already been done but Chadwick was looking for a particle with mass similar to a proton and a neutral charge. -
Werner Heisenberg
Werner Heisenberg was a German scientist who was born on December 5, 1901. The uncertainty prinicpal is like taking a picture of a moving ball. With a low shutter speed, you can calculate how fast it's going and with a high shutter speed you can see where it is. It's a trade-off. -
Thomson
J.J. Thomson was an English scientist that was born on December 18, 1856. Thomson experimented with electricity currrents in empty glass tubes, or cathode rays. He thought that corpuscles were miniscule particles that made up atoms.Thomson made his suggestion after his discovery that Lenard rays could travel much further through air than expected for an atom-sized particle. He discovered the electron. -
Atomic Radii
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