In J.J. Thomson’s experiments he was able to bend the cathode ray (which travels in a straight line) by applying either an electric field or a magnetic field. By finding the displacement of the ray he was able to calculate electric charge mass ratio the electron. And later that they were associated with the proton H+
Using the Cathode Ray Tube, he presented 3 hypotheses: • Cathode rays are charged particles • These charged particles are part of the atom. • These particles are the only constituents of the atom
Thomson’s Model of the Atom (1904) He described his atom as tiny negatively charged electrons that are embedded in a cloud of positive charge. He imagined the electrons are bits of plum in plum pudding. Today it is also explained to resemble a blueberry muffin or raisin pudding.
Prior Knowledge Remember it was J.J. Thomson who identified that the atom was composed of positive and negative charges and had proposed that the atom was a solid mass of these particles.
Significant Contributions to Atomic Theory 1900 -> 1930 • 1909 – 11 E. Rutherford, H. Geiger • 1913 R. A. Millikan • 1913 H. Moseley • 1919 N. Bohr • 1931 J. Chadwick
“It was quite the most incredible event that has ever happened in my life. It was almost as incredible as if you fired a 15 inch shell at a piece of tissue paper and it came back and hit you.” Ernest Rutherford
Neils Bohr Atomic ModelNiels Bohrapplies quantum theory to Rutherford's atomic structure.
The End of Group 3’s Presentation Next 1930’s -> ……… “Closing the book on Atomic Theory?”