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Period: 300 to
Chemistry Timeline
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460
Democritus 460BC-370BC
Democritus is born. He lives on to create the atomic theory and make the first discoveries of atoms -
John Dalton
Dalton comes up with a five part atomic theory. -
John Newlands
He published his law of octaves. Which states that “any given element will exhibit analogues behavior to the eighth element following it in the table“. Elements were arranged in 7 octaves like the musical octaves -
Mendeleev
He aranged the elements that were known at the time in order of relative atomic mass. -
William Crookes
Crookes invented the Crookes Tube and used it to discover cathode rays that had the following properties: travel in straight lines from the cathode; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge -
JJ Thomson
JJ Thomspn discovered the subatomic particle called the electron. He did this by using his famous plum pudding model and Crookes Tube. -
Ernest Rutherford
Rutherford came to the conclusion that the nucleus had a posotive charge, was very dense, and was also very small. He also made the discovery that electrons are located outside of the nucleus. -
Bohr
Bohr created a explanation of atomic structure that underlied regularities of te periodic table of elements. The atomic model that he made was composed of sucessive orbital shells of electrons. -
James Chadwick
Using alpha particles he discovered a neutral atomic particle with a mass close to a proton. This was the neutron. -
Aristotle 384BC- 322BC
Aristotle stated his theory which was that there were only four elements. The four elements were earth,air,fire and water.
