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Scientists Who Contributed to the Atomic Theory
Transcript of Scientists Who Contributed to the Atomic Theory
The experiment consists of two metal electrodes suspending droplets of oil in between them.
Knowing the charge of the field, Millikan and Fletcher could measure the charge of the droplet of oil.
mass of the electron to be 1.592 x 10^-19 coulomb
Millikan won the Nobel Prize in Physics in 1923 for his experimentation and discovery of the mass of the electron. Oil Drop Experiment calculation of the charge of the electron He discovered the neutron in 1932
Solved problem for the mass of atoms
He would bombard the atoms with alpha rays which are charged, and therefore repelled.
This new tool in atomic disintegration need not overcome any electric barrier and is capable of penetrating and splitting the nuclei of even the heaviest elements.
Chadwick paved the way towards the creation of the atomic bomb.
Awarded the Hughes Medal of the Royal Society in 1932, and the Nobel Prize for Physics in 1935 1891-1974 Discovery of the neutron Max Planck 1848-1947 He gained recognition for his work after Albert Einstein used Planck’s constant h to determine the photoelectric effect.
Niels Bohr applied the principle to the atom superseding Ernest Rutherford's atomic model General Work
(Quantum Mechanics) He was regarded as the pioneer of quantum mechanics, in which he proposed Planck’s constant h.
Planck tries to explain the pattern of light intensity emitted from a black body
This new concept formed the foundation for quantum mechanics. Planck's Constant and Black Body Radiation Planck’s constant- E=f*h, where h is 6.63 * 10E-34 Js
E: energy of each quantum
f: frequency of the radiation
h: universal constant
The “black body” is referring to the radiation/energy that is emitted by heated materials.
Concluded energy is not a continuous, flowing entity, but is carried in tiny, discontinuous units, which he named quanta Base for Future Scientists 1871-1937 Ernest Rutherford JJ Thomson Participation in Atomic Theory Thomson concluded that atoms have different isotopes when he was working with canal rays.
He shot a beam of neon through an electromagnetic field, measuring it with a photographic plate.
The neon was deflected into two separate beams, confirming the existence of isotopes.
This is the first use of mass spectrometry. Electrons and the Plum Pudding Model Thomson discovered the electron (corpuscles) during his experiments with cathode rays.
Cathode rays were deflected off of an electrically charged plate.
He then calculated the mass-to-charge ratio, which Robert Millikan used to find the actual mass.
Hypothesized that atoms were divisible
Said the atom was a sphere of positive matter, protons, surrounded by the electrons in an electrostatic field. (Plum pudding model) Other Discoveries isotopes and mass spectrometry http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::100%25::100%25::/sites/dl/free/0072512644/117354/01_Cathode_Ray_Tube.swf::Cathode%20Ray%20Tube Video
http://www.thebigview.com/spacetime/quantumtheory.html Sources All James Chadwick Robert Millikan JJ Thomson Max Planck Videos Ernest Rutherford 1856-1940 Niels Bohr Einstein 1868-1953
American Physicist Timeline 1902-radioactivity is a manifestation of sub-atomic change
1903-shows how atoms radioactively decay at different rates, coins term "half-life"
1906-proposes atom's structure is nuclear
1908-wins Nobel Prize
1911-describes in detail the nuclear model of the atom
1913-uses cathode ray bombardment to show how atom's structures can be used to assign an atomic number to each element
1914-describes the proton
1917-creates nuclear physics by experimenting with nuclei and their radioactivity
1917-first scientist to ever split an atom Gold Film Experiment proving nuclear model of atom Proving that the atom was composed of positive and negative charges.
Charges were in some arrangement that left empty space in the atom,
Since the gold film was so thin, Rutherford proposed that all of the deflections observed were from single encounters of alpha particles (nuclei of helium atoms) with the atom. In order to deflect the relatively large and swiftly moving alpha particles to such a large extent, a large force was required.
This force, he contended, could only be caused by a large concentration of positive charge within the atom. This large concentration of charge was located at the center of the atom and became known as the nucleus. The negative charge, in the form of electrons, was then distributed throughout the rest of the space occupied by the atom.