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Democritus
Democritus was an ancient greek philosopher. He thought that atoms were indivisible and indestructable. Even though he was right, no one believed him because he lacked experimental proof. Technology wasn't advanced far enough for him to prove his theory about the atom. It would be alomst 1400 years until his theory would be proven correct. -
John Dalton
John Dalton was an english chemist that expanded on Democritus' theory. Dalton started his own atomic theory. Unlike Democritus, Dalton has experiments to back up his theory. His atomic theory is composed of 4 parts: 1. All atoms are are tiny indivisible particles. 2. Atoms of the same element are identical, but aren't the same as other elements. 3. Atoms can mix chemically and physically to form compounds. 4. Chemical reactions occurr when different atoms seperate, join, or rearrange in combina -
J.J. Thomson
Thomson was an english physicist who discovered the electron. Thomson discovered that electron by using a cathode ray tube, He also discovered that the electron had a negative charge. When using the cathode ray tube, he discovered that the positively charge plate was attracted to the ray. -
Eugen Goldstein
Eugen Goldstein was a German physicist that discovered the proton and its positive charge. Goldstein discovered that rays in a cathode tube traveled the opposite direction of the electron rays. This showed that the proton was positively charged. The proton has the mass of about 1840 times the size of the electron. -
Robert Millikan
Robert Millkan was a US physicist that expanded on Thomson's data. He used the oil drop experiment to calculate the mass and charge of the electron. The oil drop experiment was where he put a charge on the oil drop and then measured the charge it produced. He concluded that the electrons charge wa 1.60 X 10^-19 columbs, and the mass was 1/1840 the mass of hydrogen. -
James Chadwick
James Chadwick was an english physicist that discovered the last subatomic prticle. He discovered the no charged particle known as the neutron. He also discovered that the neutron had almost the same mass as a proton. -
Ernest Rutherford
Ernest Rutherford was a British physicist that discovered the correct diagram of the atom. He did this by his gold foil experiment, and discovered that the atom was mostly empty space. When he fired alpha particals at a thing piece of gold foil and saw that the angles deflected. This showed his that atoms were mostly open space.
