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4000 BCE
400 B.C. Democritus
Democritus theory posited that all matter is made up small indestructible units he called atoms. -
John Dalton
John Dalton proposed that elements consisted of atoms that were identical and had the same mass and that compounds were atoms from different elements combined together. -
1897 J.J. Thompson
J.J Thompson determined the charge to mass ratio of electrons. -
Ruthford
Rutherford discovered the atomic nucleus, using a "scattering" experiment, diagramed at right, that would become a classic technique of particle physics. -
Niels Bohr
Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities. Electrons should move around the nucleus. -
Sir James Chadwick (1932)
He was an English expert in physics who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932. He was the head of the British team that worked on the Manhattan Project during the Second World War. He was recognised in England in 1945 for his achievements in physics! -
Current Model
The Current Model of the atom is in the image to the left.
