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101
Democritus - 429 BC
First person to think of the atom.
Thought the atom was a solid circle. -
Issac Newton
Tiny pieces of mass "swimming" everywhere
(he agreed with Democritus) -
John Dalton
All matter is composed of atoms - true
Atoms cannot be made or destoryed - false; an atom can be split
by a nuclear reaction
All atoms of the same elements are idenctical - false; isotopes
Different elements have different types of atoms - true
Chemcial reactions occure when atoms are rearranged - true
Compunds are formed from atoms of different elements - true -
Henri Becquerel
Helped discover radioactivity -
J.J Thomson
Proved the existence of negatively charged atoms ( electrons ) -
Andrew Milikan
Measured charge and mass of electron. -
Rutherford
An atom has a central positive nucleus surrounded by negative orbiting elements.
He was credited with the nucleus and proton. -
Bohr
His electrons are traveling in orbits.
Decided atom was a small, positively charged nucleus surrounded by electrons. -
Francis Aston
Discovered isotopes of non-radioactive elements. -
Schrodinger
Found the atom consist of nucleus aned cloud.
Discovered the formula that calculated the odds of where the electron might be.
Proved Bohr's model incorrect. -
James Chadwick
Discovered the nuetron. -
Aristotle - 400 BC
Thought everything was made up of fire, air, earth, and water instead of atoms