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Transcript of Democritus
Democritus - 1st Oct, 0400 (Greek Era)
Democritus found the atom. All atoms are indivisible. Atom derives from atomos. Atomos is greek for indivisible.
He described atoms as ball of positive charge containing a number of electron, discovered the electron. Used a CRT to experimentally determine the charge to mass ratio (e/m) of an electron =1.759 x 10 8 coulombs/gram. Studied "canal rays" and found they were associated with the proton H + .
J.J. Thomson - 1897
He proposed atomic theory, with spherical solid masses in motion. Atoms can't be made or destroyed.
John Dalton - 1803
Neils Bohr - 1922
He is the Father of Quantam theory, Proposed that the atom is "successive or bital shells of electrons. Bohr came up with the "Bohr Planetary Model."
He is the father of nucleus physics. He developed the "gold foil experiment." Rutherford determined that the nucleus of an atom is very dense and has a positive charge.
Ernest Rutherford- 1926
Wilhelm Roentgen - 1845
While using a CRT, he observed nearby chemicals that glowed. Some of the rays weren't deflected by the magnetic field.
James Chadwick - 1932
Chadwick proved the existence of neutron. He discovered a particle within the nucleus that has a mass similar to that of a proton.
Lise Meitner, Hahn, Strassman - 1938
Conducted experiments verifying that heavy elements capture neutrons and form unstable products which undergo fission. This process ejects more neutrons continuing the fission chain reaction.
Ernest Lawrence - 1936
He invented the cyclotron and recognized the potential for medical isotopes. Isotopes are used to make medicines. When radioactive isotopes are introduced to the body, they give off an energy or radiation that can be tracked by imaging equipment. This allows doctors to more efficiently pinpoint exactly where the diseased tissue is. Image scanning using radioactive isotopes is more finely detailed and more accurate than MRI scans.
First Atomic Bomb dropped- 1945
The atomic bomb was dropped to finish World War 2. America used Cockroft and Walton's idea, and split the atom to create a nuclear bomb.