Atomic Theory 1

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Atomic Theory 1
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What Happens in Vegas stays in Vegas
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Atomic Theory Theories in science are proposed
to explain the evidence available at the time.
As new evidence is discovered theories are
adapted to explain new data. This is the nature
of Science. In the future this will continue.
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Plato
Democritus
460-370 BC
Atoms make up the world
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Plato
Teacher of Aristotle
Aristotle
384-322 BC
Four Elements
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The Four Element Theory
Properties
Forces
Aristotle
wetness
conflict
harmony
Water
Wind
coldness
hotness
Fire
Earth
dryness
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The Four Element Theory lasted for about 2
thousand years because no one tested the theory
with scientific experiments.
It was not a scientific theory- which is tested
by experiment.
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John Dalton
1766-1844
Atomic Theory
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Daltons Atomic Theory- 1808 Evidence 1. The
Law of Conservation of Mass 2. The Law of
Constant Composition- water is 11 H and 89
O Theory 1. Each atom is an indestructible and
unique spherical particle 2. Atoms combine in
simple whole number ratios to form compounds
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Hydrogen
Oxygen
Lithium
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Dalton Theory- Water
1 g H
1 g H
16 g O
18g O
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Dalton Theory- Water
18g O
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Dalton Theory- Water
2 g H
11 H
x 100
89 O
18 g H2O
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Having a molecule (atoms combine in simple whole
ratios) explains the law of constant
composition.
Still 11 H 89 O
No matter how much water you have its still 11 H
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2H2 O2 ? 2H2O
If the atoms are not destroyed then the mass does
not change
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J. J. Thomson 1871-1937
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The Thomson Theory of the Atom Evidence 1. The
electrical nature of matter beta
particles static electricity current
electricity Theory 1. The atom is made up of
positive material with negative particles
throughout- like blueberries in a blueberry
muffin.
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The Thomson Atom 1903
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Ernest Rutherford 1871-1937
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The Rutherford Atom 1911 Simulation Evidence
Gold Foil Experiment 1. 99.99 of alphas are not
deflected 2. 0.01 of alphas are radically
deflected Theory 1. Most of the atom is empty
space. 2. There is a small dense nucleus in the
center of the atom that makes up most of the
mass. Electrons circle the nucleus randomly.
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The Rutherford Atom 1911 Scale nucleus is home
plate atom is the baseball field
Be
Nucleus- is small but has most of the mass

Nucleus- 4 protons and 5 neutrons
Electrons
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Cornelis Escher 1898-1972
Discovery of the Nucleus
Size of the Atom