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101
Democritus - 429 BC
1st person to think of the atom.
Thought atom was solid circle. -
101
Aristotle - 400 BC
Earth is composed of four elements water, fire, air, and earth. -
Isaac Newton
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John Dalton
All matter is composed of atoms - T
Atoms cannot be made or destroyed - F
All atoms of the same element are identical - F
Different elements have different atoms - T
Chemical reactions occur when atoms are rearanged - T
Compounds are formed from atoms of diff elements -T -
Henri Becquerel
Helped discover radioactivity. -
J. J. Tomson
Proved existence of electrons. -
Cathode Ray Tube
Was a tube of nothing hooked up to an electric charge. A beam of light resulted JJ held up a magnet to the beam and found the beam was charged. -
Robert Millikan
Measured a charge and mass of electroms. -
Rutherford
An atom has a central positive nucleus surrounded by negative orbiting electrons. -
Bohr
Depicted a small positive nucleus surrounded by electrons are traveling in orbits. -
Iransis Aston
Discovery of Isotopes of non-radioactive elements. -
Schrodinger
Atom consisted of nucleus and shells.
Proved Bohr model incorrect. -
James Chadwick
Discovered the neutron.