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Democritus Atomic Theory
1)
2)
3)
4)
5)
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All matter is composed of atoms, which are bits of
matter too small to be seen
These atoms CANNOT be further split into smaller
portions
There is a void, which is empty space between
atoms
Atoms are completely solid
Atoms are homogeneous, with no internal
structure
Atoms are different in their sizes, shapes, weight,
arrangement, position…
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John Dalton (1766~~1844)
¾ A New System of
Chemical Philosophy
¾ Developed the first
useful atomic theory of
matter
¾ Gifted in for recognizing
and interpreting patterns
in experimental data
¾ First to associate the
idea of atoms with
stoichiometry
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Dalton’s Atomic Model
1.
2.
3.
4.
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All matter consists of tiny particles
Atoms are indestructible and
unchangeable
Elements are characterized by the mass
of their atoms
When elements react, their atoms
combine in simple, whole-number
ratios
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J. J. Thomson ( 1856~~1940)
Discovered electrons
in 1891.
Cathode ray tubes
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A Cathode Ray Tube
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(1871~~1937)
Discovered the nucleus
in 1911
The gold foil experiment
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Rutherford’s solution to the enigma
of explaining both large- and
small-angle scattering, was the
nucleus
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All Rutherford had to do was explain how
it all fit together
Well established that atomic radius is 10-8 cm
Thomson model spread the entire mass of the atom
throughout that space
Rutherford put most of the mass of the atom at the
center of the atom, in a space much, much smaller
that the atom itself
this is the
nucleus
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Empty space!!
If an atom were the
size of a baseball
stadium,
The nucleus would
be the size of a
PEA
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Structure of the Nucleus
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A Model of Helium
2 protons
2 neutrons
2 electrons
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Elements Chart
Element
Symbol
Atomic
#
Atomic
Mass
Mass
#
#
Protons
#
Electrons
#
Neutrons
H
1
1.008
1
1
1
0
He
2
4.003
4
2
2
2
O
8
N
7
C
6
F
9
P
15
Sn
50
C-14
6
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Isotopes
Same Atomic Number, Different Atomic Mass
Same # of Protons, Different # of Neutrons
Hydrogen:
Heavy Hydrogen
1 proton, 0 neutrons
1 proton, 1 neutron
(Deuterium):
Heavier Hydrogen
(Tritium):
Carbon~12:
Carbon~14:
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1 proton, 2 neutrons
6 protons, 6 neutrons
6 protons, 8 neutrons
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Alkali Metals
Boron Family
Nitrogen Family
Halogens
Alkaline Earth Metals
Carbon Family
Oxygen Family
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Transition
Metals
Noble Gases25
Democritus~~Rutherford
gas
liquid
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Source of Images and Text
http://antoine.frostburg.edu/chem/senese
/101/atoms/dalton.shtml
http://dbhs.wvusd.k12.ca.us/RutherfordModel.html
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