history of the atom. democritus (400 bc) proposed that matter was composed of tiny, invisible...
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History of the Atom
Democritus (400 BC)
• Proposed that matter was composed of tiny, invisible particles.
• Gr. atomos
Aristotle
• Said that all substances are composed of four elements: Earth, Wind, Fire, and Water.
John Dalton (1803 AD)• the first coherent atomic theory
• Matter is composed of small particles called atoms.
• All atoms of an element are identical.
• During chemical reactions, atoms are neither created nor destroyed, but are simply rearranged.
J.J. Thompson (1897 AD)
• Used cathode rays to calculate the atomic mass of atoms.
Cathode Ray Tube Experiment
Ernest Rutherford (1910 AD)
• alpha particles (He nuclei) were shot at a thin piece of gold foil.
• most of the particles passed through the foil with little or no deflection, some were deflected to a great degree.
Gold Foil Experiment
Isotopes
Radioactive Decay
C14 Decay
Carbon Dating
Carbon Dating VideoClick on the picture above to view.
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