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Democritus
Democritus proposed that everything around us is made up of atoms.He also said that they can't be divided, can't be destroyed, and that they hve always been around. This happened in the 5th century B.C. -
Antoine Lavoisier: Law of Conservation of Mass
Antoine Lavoisier weighed products and reactant and found out that the mass was the same as before and after. Even though it changed form nothing was lost or gained in the process. -
John Dalton: Dalton's Atomic Theory
John Dalton said that everything is made up of small particles called atoms. Also that atoms of the same element are the same, but that different element atoms differ in appearance. He stated that atoms cannot be destryed, created, or divided. If different elements combine , it is called a chemical compound. In a chemical reaction atoms can be combined or seperated. -
Dmitri Mendeleev
Dmitri Mendeleev created the Periodic Table of elements. At the time there were only 56 known elements -
Dmitri Mendeleev
Dmitri Mendeleev created the Periodic Table of Elemnts. At the time ther were only 56 known elements. He arranged them in order of their atomic weight. -
J.J. Thomson: Cathode Ray Tube
J.J. Thomson performed the cathode ray tube experiment twice. The first time he had rays shot out from and electron gun to show that they couldnt be seperated from latent charge. It could measure small electric charges. In the second expereiment he tried to prove that the rays carried a negative charge. -
J.J. Thomson: Plum Pudding Model
J.J. Thomson discovered the electron in 1897. The plum pudding model showed the electrons randomly scattered throughout the atom. -
Robert MIlikan
Robert Milikan did and oil-drop experiment. The point of this experiment was to measure the charge of one single electron. He won the Nobel Prize for Physics. -
Ernest Rutherford: Gold Foil Experiment
Ernest Rutherford began his research of the alpha particles in 1909. He was the first to notice that it didn't match up with the plum pudding model. He and some associates beamed a ray of alpha particles at a piece of gold foil. According to the plum pudding model they should have passed staright throug,bu they didn't. -
Ernest Rutherford: Rutherford Model
Ernest Rutherford discovered all the componets of the atom: nucleus, protons, and electrons. The nucleus is placed in the middle and that the electron and protons circled it. -
Henry Mosely
Henry Moseley discovered that he could measure elements through the X-ray spectra. This started the X-ray spectroscopy. He discovered the relatioonship between wavelengths and atomic numbers. -
Niels Bohr:Electron Cloud Model
Niels Bohr discovered that all the mass of an atom came from the nucleus and the electrons were in a synchronized orbit. The faster they went the more radiation came out. He said that the outer levels of the atom could hold more electrons than the inner levels. -
Erwin Schrodinger
Erwin Schrdinger published a book over wave mechanics. It was a start of quantum mechanics. -
James Chadwick
James Chadwick discovered the neutron that is located in the nucleus. It has a neutral charge. He was then awarded the Hughes Medal of the Royal Society in 1932. His discovery made it possible to make heavier elements in the lab.
