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First person to think of the atom
Thought atom was a solid circle -
Proposed that everything was made up of air, fire, earth, and water.
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Believed there were pieces of mass floating everywhere.
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Dalton's Atomic Theory:
1. All matter is composed of atoms - True
2. Atoms cannot be made or destroyed - True
3. All atoms of the same elements are identical - False
4. Different elements have different types of atoms - True
5. Chemical reactions occur when atoms are rearranged - True
6. Compounds are formed from atoms of different elements - True -
He helped discover radioactivity
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Proved the existence of negatively charged particles, later called electrons.
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Measured the charge of an electron
Measured the mass of an electron -
Found that an atom has a central positive nucleus surrounded by negative orbiting electrons
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Depicted atom as small, positively charged nucleus surrounded by electrons
Electrons travel in circular orbit -
Discovered isotopes of non-radiactive elements
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Atom consists of nucleus and clouds
Discovered formula that calculated where an electron might be -
Discovered neutron
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