Download Notes Atomic Theory 013117

The Development of the Modern Atomic Theory
Democritus
o ~460BC – 370BC
o 1st to say that all matter is made of tiny, indivisible
particles called atomos (atoms).
o Less popular that Aristotle
 All matter is made of earth, air, water, & fire.
John Dalton
o 1766 – 1844
o Dalton’s Atomic Theory
 All matter is made of tiny, indivisible particles
called atoms.
 All atoms of a given element are identical.
 Compounds are combinations of 2 or more
elements.
 Chemical reactions are the rearrangement of
atoms.
JJ Thomson
o 1856 – 1940
o Cathode Ray Experiment in 1894 – discovered
negatively charged particles in the nucleus, called
electrons
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o Plum Pudding Model (Chocolate Chip Cookie)
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Ernst Rutherford
o 1871 – 1937
o Gold Foil Experiment in 1911 – discovered the
positively charged nucleus in the atom
o
o Discovered the positively charged protons in the
nucleus in 1917.
o Rutherford Model
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James Chadwick
o 1892 – 1974
o Worked as a graduate student under Rutherford
o Discovered neutrons in the nucleus in 1932
Niels Bohr
o 1885 – 1962
o Bohr Model (Planetary Model)
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Erwin Schrödinger
o 1887 – 1961
o Quantum Mechanical Model
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