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Atomic scientist timeline project

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Timothy Huffman

on 9 October 2013

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Transcript of Atomic scientist timeline project

Atomic Scientist Project
by: Timothy Huffman

Robert Millikan
Birth- March 22, 1868 Death- December 19, 1953
James Chadwick

Birth: October 20, 1891 Death - July 24, 1974
J.J Thomson
Brief description
Joseph John Thomson is widely recognized as the discoverer of the electron. For much of his career, Thomson worked on various aspects of the conduction of electricity through gases. In 1897, he reported that "cathode rays" were actually negatively charged particles in motion.

He argued that the charged particles weighed much less than the lightest atom and were in fact constituents of atoms. In 1899, he measured the charge of the particles, and speculated on how they were assembled into atoms.
Birth- December 18, 1856

Death- August 30, 1940
Photo of experiment
Brief Description

It measures the elementary electric charge (the charge of the electron).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.
Using a known electric field, Millikan and Fletcher could determine even the charge on oil droplets in mechanical equilibrium. By repeating the experiment for many droplets, they confirmed that the charges were all multiples of some fundamental value, and calculated it to be 1.5924(17)×10−19 C, within 1% of the currently accepted value of 1.602176487(40)×10−19 C. They proposed that this was the charge of a single electron.It
Ernest Rutherford
Brief description
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 conclude information about the structure of the foil.

How their experiment revolutionized the atomic theory and the way we think about the atom?
Rutherford made the atomic theory in 1919, when he was working for J.J. Thompson. He found the atomic nucleas but he also made it so that people knew what matter is made up of.

Born: March 22, 1868 -Died: December 19, 1953
How their experiment revolutionized the atomic theory and the way we think about the atom.
Brief description
With Chadwick's announcement, Heisenberg then proposed the proton-neutron model for the nucleus. Rutherford was incorrect in his "proton-electron" pair there were no "free electrons" in the nucleus. Wolfgang Pauli proposed in 1930 the existence of an invisible particle that would carry off the missing energy and momentum. He called this particle the neutrino, or little neutral one.

In 1932, Chadwick proposed that this particle was Rutherford's neutron. In 1935, he was awarded the Nobel Prize for his discovery. Using kinematics, Chadwick was able to determine the velocity of the protons.

How their experiment revolutionized the atomic theory and the way we think about the atom?
Dalton's atomic theory reveals that atoms are indivisible (meaning atoms cannot be broken any further into smaller particles), but because J.J Thomson proved that electrons exist, J.J recommended that atoms are divisible. This changed Dalton's theory because Dalton's theory suggested no subatomic particles (protons, nutrons, electrons) are present but through the cathode ray tube experiment, Thomson found that atoms can be broken down further into further subatomic particles, which contradicted Dalton's theory.
Photo of experiment
How their experiment revolutionized the atomic theory?
He determined the charge on electrons.
Photo of experiment
Rutherford expected all of the particles to be deflected just a bit as they passed through the plum pudding. He found that most of the a’s he shot at the foil were not deflected at all. They passed through the foil and emerged undisturbed. Occasionally, however, particles were scattered at huge angles. While most of the a’s were undisturbed, a few of them bounced back directly. Imagine if something like this happened at our mound of snow. We shoot bullets at the pile for days, and every round passes straight through, unperturbed then a bullet hits the snow, reflects back, and splinters the gun’s stock! Rutherford’s result lead him to believe that most of the foil was made of empty space, but had extremely small, dense lumps of matter inside. With this experiment, Rutherford discovered the nucleus.
photo of experiment
Atoms are electrically neutral because the number of protons (+ charges) is equal to the number of electrons (- charges) and thus the two cancel out. As the atom gets larger, the number of protons increases, and so does the number of electrons (in the neutral state of the atom).
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