Atomic Scrience Project

J.J.Thomson

Dec 18, 1856

August 30, 1940

Robert Millikan

Mar 22, 1868

Ernest Rutherford

Aug 30, 1871

James Chadwick

Oct 20, 1891

J.J.Thomson Experiment

May 30, 1897

If a gas sample is introduced into the region between two charged plates, a current flow can be observed, suggesting that the atoms have been broken down into charged constituents. The source of these charged particles is a heated cathode that, in fact, causes the atoms of the sample to ionize. These were known as cathode rays. In 1897, Thomson set out to prove that the cathode rays produced from the cathode were actually a stream of negatively charged particles called electrons.

Millikan Contribution to Atomic Theory

Feb 13, 1899

Millikan had great contribution to the Atomic Theory. He performed the Oil drop Experiment. This helped in determining the charge and mass of an electron.

J.J. Thomson Contributions to atomic theory

Oct 27, 1904

J.J. Thomson's contribution to the atomic theory is that he was able to identify the existence of electrons in an atom. The meant that atoms are not invisible and could be seen. His theory also suggested that atoms where spherical and had a positive charge.

Robert Millikan Experiment

Jun 9, 1909

The experiment entailed balancing the downward gravitational force with the upward drag and electric forces on tiny charged droplets of oil suspended between two metal electrodes. Since the density of the oil was known, the droplets' masses, and therefore their gravitational and buoyant forces, could be determined from their observed radii.

Rutherford Contributions to Atomic Theory

Apr 13, 1911

Ernest Rutherford atomic theory leads to his belief that an atom was mostly empty space. He believed the atom had a central nucleus. This nucleus was surrounded by electrons that were negative and orbited the atom

Ernest Rutherford Experiment

Sep 5, 1911

In 1911, Ernest Rutherford performed an experiment to test the plum pudding model. He fired energetic a [He2+] particles at a foil, and measured the deflection of the particles as they came out the other side. From this he could deduce information about the structure of the foil. To understand how this works, imagine shooting a rifle at a mound of loose snow: one expects some bullets to emerge from the opposite side with a slight deflection and a bit of energy loss depending on how regularly the

James Contributions to Atomic Theory

Sep 11, 1935

James Chadwick contributed to atomic theory by his experiments proving the existence of neutrons. He won the Nobel Prize in 1935 for his discovery.

James Experiment

Oct 2, 1935

Rutherford described his 'neutral doublet', or neutron, in 1920. The particle would be uncharged but with a mass only slightly greater than the proton. Because it was uncharged there would be no electrical repulsion of the neutron as it passed through matter, so it would be much more penetrating than the proton. This would make the neutron difficult to detect.

Ernest Rutherford

Oct 19, 1937

J.J.Thomson

Aug 30, 1940

Robert Millikan

Dec 19, 1953

James Chadwick

Jul 24, 1974