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Big Ideas
Structure & Properties of Matter
 The
nature of the attractive forces that exist
between particles in a substance determines
the properties, and limits the uses of that
substance
 Technological
devices that are based on the
principles of atomic and molecular structures
can have societal benefits and costs
Atomic Theory
•
the theory that all matter
is made up of tiny
indivisible atoms
•
atoms of each element
are effectively identical,
but differ from those of
other elements, and
unite to form compounds
in fixed proportions
http://www.youtube.com/watch?v=yQP4UJhNn0I
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The Atomic Model
 What
 The
does an atom look like?
answer to this question has evolved
over many years…
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Democritus
460 BCE – 370 BCE
•
Ancient Greek philosopher
who proposed that if an
object was cut-in-half over
and over again, eventually
you reach a point at which
it could not be cut-in-half
anymore
•
This piece was said to be
indivisible or (ἄτομος;
“atomos”)
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John Dalton
1803
-
Matter divided into small,
indivisible atoms
Each elements made of
different atoms
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Dalton’s Billiard
Ball Model
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JJ Thomson
1897
-
discovered positive/negative
charges within atom
-
Cathode Ray Tube Experiment:
-
http://www.youtube.com/watch?v
=2xKZRpAsWL8
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JJ Thomson’s
Raisin Bun Model
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Ernest Rutherford
1911
-discovered negative electron
cloud surrounding central,
positively charged nucleus
Gold Foil Experiment
http://www.youtube.com/watch
?v=wzALbzTdnc8
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Rutherford’s
Beehive Model
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Niels Bohr
1913
-described surrounding
electrons to be locked into
“orbits” of specific energy
levels
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Bohr’s Solar
System Model
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Quantum Mechanics
17 of the 29 attendees were, or became, Nobel
Prize Winners
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Quantum
Mechanical
Model
•
•
•
It turns out, that all those
models were incomplete
This is where the electrons
really are…
--------------------------
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Quanta – plural
Quantum – singular
•
•
•
•
•
Atoms & electrons, cannot be seen, only modelled
They are modelled by the way that they respond to
energy (electormagnetic) input
Energy is given to the particles (atoms/electrons etc)
and the response is detected
Hypotheses are formulated which are then tested by
all available means
If the experimental evidence seems to fit the
hypothesis then a theory is proposed which in time
comes to be accepted as the "truth“ or the
“accepted model”
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The Photon
 1873:
James Maxwell proposes that light is
an electromagnetic wave that can exert
forces on charged particles.
 Earlier scientists including Isaac Newton felt
that light should be studied as particles
 1887: Heinrich Hertz discovers the
photoelectric effect
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Bohr & Hydrogen

Bohr excited electrons with light (photons)

http://www.ibchem.com/IB/ibfiles/atomic/ato_swf
/line_spec.swf