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101
Democritus - 429 BC
First person to think of the atom.
Though atom was a solid sphere. -
102
Aristotle - 400 BC
Proposed everything was made from fire, air, water, and earth instead of atoms. -
Sir Issac Newton
Believed that there was little pieces of mass that were "swimming' everywhere. -
John Dalton
- all matter is comosed of atoms (True)
- atoms cannot be made or destroyed (False)
- all atoms of same element are identical (False)
- different elements have different types of atoms (True)
- chemical reactions occur when atoms are rearranged (True)
- compounds are found from atoms of different elements (True)
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Henri Becuerel
He helped discover radioactivity. -
Joseph John Thomson
Proved the exsistence of negatively charged particles, later called electrons. -
Robert Andrews Millikan
He measured the charge of a single electron and mass. -
Ernest Rutherford
An atom has a central postive nucleus surronded by negative orbiting electrons. Credited with nucleus and proton. -
Neils Bohr
Depicted atom as small, postively charged nucleus surronded by electrons. Electrons travel in circular orbit. -
Francis Aston
Discovered isotopes of non-radioactive elements -
Erwin Schrodinger
atom consists of nucleus and clouds. Discovered formula that calculated the odds of where an electron might be. Proved Bohr Model incorrect -
James Chadwick
Discovered neutron.