Download History of Atomic Theory

Atomic Theory
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Label the 3 different particles that make
up an atom
What is the charge of each?
Draw a model of the element Boron (B)
Development of atomic theory
Democritus
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Atoms are
indivisible,
indestructible,
fundamental units of
matter.
“Atomos”
Never went further
than this
Aristotle
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Four elements of air,
earth, water and
fire.
Regardless of the
number of times you
cut a form of
matter, you would
always have a
smaller piece of that
matter.
Dalton’s Atomic Theory
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1. All matter is composed of extremely
small particles called atoms.
2. Atoms of given elements are
identical in size, mass, and other
properties.
Dalton’s Atomic Theory
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3. Atoms can not be subdivided,
created, or destroyed.
4. Atoms of different elements can
combine in simple, whole-number ratios
to form chemical compounds.
Dalton’s Atomic Theory
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5. In a chemical reaction, atoms are
combined, separated, or rearranged.
Example:
 H2 + O2  H20
William Crookes
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Discovered
cathode rays
Set the stage
for
JJ Thompson
and his
discoveries
J. J. Thomson
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Discovery of the
electron
Cathode ray tube
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Positively charged ions, called cations, move towards
the cathode
Negatively charged ions, called anions, move
towards the anode.
J. J. Thomson’s Model
Robert Millikan
oil drop experiment
- calculated the mass of the electron
Ernest Rutherford
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Existence of the
nucleus and its
relative size
Gold foil experiment
Rutherford’s Gold Foil
Experiment
Rutherford’s Gold Foil
Experiment
James Chadwick
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Discovered the last known subatomic particle
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The neutron which has no charge
No. Not this Neutron…
This neutron.