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460
Democritus
Link Location: Greece Idea/Experiment:He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further? Contribution: He was the first person to develop the idea of atoms. -
Period: 460 to
Year
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Newtown
Link Location: England Idea/experiment:Raised the question of creation as a result of pure chance which traditional atomic theory implied. Contribution: His theory is very close to our atomic theory we have today. -
Dalton
Link Location: England Idea/experiment:Performed experiments with various chemicals that showed that matter seemed to consist of elementary lumpy particles (atoms). Contribution: He confirmed that matter consisted of atoms. -
G.J. Stoney
Link Location: Ireland Idea/experiment:Proposed that electricity was made of negative particles called “electrons”. Contribution: Found that electricity was made of negative particles. -
J.J. Thomson
Link 2#Link 1# Location: England Idea/experiment:Thomson found that the mysterious glowing stream in the cathode ray tube would bend toward a positively charged electric plate. He theorized that the stream was made up of small particles, pieces of atoms that carried a negative charge. Contribution:Discovered the electron and made a model for the structure of the atom -
Planck
Link Location: German Idea/experiment:His idea was that an oscillator could emit energy only in discrete quanta, contrary to classical physical theory Contribution: Showed that when you vibrate atoms strong enough, such as when you heat an object until it glows, you can measure the energy only in discrete units. He called these energy packets, quanta. -
Nagaoka
Link Location: Japan Idea/experiment:He proposed an alternative model in which a positively charged centre is surrounded by a number of revolving electrons, in the manner of Saturn and its rings. Contribution: He was the first person who found that a positively charged centre is surrounded by a number of revolving electrons. -
Millikan
Link Location: American Idea/experiment:Millikan measured the charge on an electron with his oil-drop apparatus. Contribution: He proved Thomson's hypothesis that the mass of an electron is at least 1000 times smaller than the smallest atom. -
E. Rutherford
Link Location: England Idea/experiment:Ernest Rutherford thought it would prove interesting to bombard atoms with these alpha rays, figuring that this experiment could investigate the inside of the atom. He used Radium as the source of the alpha particles and shinned them onto the atoms in gold foil. Contribution: He was the first person to identify the particles of the nucleus. The 6 elements: B, F, S, Al, P and N. -
H.G.J. Moseley
Link Location: England Idea/experiment: He conducted an experiment where he studied the frequencies of the x-rays given off by cathode-ray tubes when electrons strike the anode. Contribution: Found that there was a relationship between the frequencies (v) of the x-rays given off by the cathode-ray tube and the atomic number of the metal used to form the anode. -
Bohr
Link Location: Denmark Idea/experiment: His idea was that the electrons do not spiral into the nucleus and came up with some rules for what does happen. Contribution: Made the model that described the electrons as orbiting in discrete, precisely defined circular orbits. -
James Chadwick
Link Location: England Idea/experiment:James based his discovery on Rutherford’s idea: That there was such thing as a neuron. Contribution: He was the first person who discovered the neuron.
