Download DEVELOPMENT OF ATOMIC THEORY

ATOMIC THEORY OF MATTER
DEVELOPMENT OF
ATOMIC THEORY
•Matter
is made up of
fundamental particles
called atoms
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ANCIENT GREECE
• Four
elements
DEMOCRITUS
• Greek
Philosopher (~ 400 B.C.)
parts of matter
• not divisible
• **Matter was empty space and atoms.
• **Each type of matter had its own type of atom
• Did not test their ideas with experiments
• “Atomos” smallest
• Fire
• Air
• Water
• Earth
• Other
Greek philosophers disagreed with
Democritus
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LAVOISIER’S
LAW CONSERVATION OF MASS
• Total
mass of a reactants must be
the same as mass of products
• “Matter
cannot be created or
destroyed”
• Atoms
• 1782
are “recycled”
PROUST’S LAW
DEFINITE PROPORTIONS
• Elements
occur in specific ratios
(proportions) in substances
• Proportions
• Ex:
-
• significance
are always the same
CO2
• 1799
in history??
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www.wise.k12.va.us/ jjk/Chemistry/dalton2.gif
www.nndb.com
www.wise.k12.va.us/ jjk/Chemistry/dalton2.gif
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DALTON’S THEORY
JOHN DALTON
•Early
• All
matter is composed of tiny
indivisible particles called atoms
1800s
•English
• All
•Studied
the work of
Lavoisier and Proust
•First complete
atomic theory
www.learner.org
atoms of one element are exactly
alike, but atoms of different elements
are different from each other
• Atoms
are neither created or
destroyed in any chemical reaction
(Lavoisier) & Compounds always have
the same ratio of elements (Proust).
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HYPOTHESES,LAWS, THEORIES
HYPOTHESES,LAWS, THEORIES
• Law:
• Hypothesis:
• Possible explanation for an
observation of something in
the natural world - must be
testable
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• Observation about nature
that has been repeated and is
predictable.
• Does not provide any
explanation.
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HYPOTHESES,LAWS, THEORIES
• Theory:
• Possible explanation that
has been supported by a lot
of observations and
experiments.
• Remains a valid theory
until disproven.
DISCOVERING PARTS OF
THE ATOM
SOME SCIENTISTS SUSPECTED THAT
ATOMS CONTAINED EVEN SMALLER
PARTICLES.
THESE ARE THEIR STORIES :)
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ELECTRONS
• J.J.
ELECTRONS
Thomson
• 1890s,
• J.J.
English
Thomson
• “Plum
Pudding” or
“Raisin Bun” model
• Discovered
first
subatomic particle (e-)
dwb.unl.edu/.../demos/jpeg/cath7.jpg
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dwb.unl.edu/.../demos/jpeg/cath7.jpg
CATHODE RAY TUBES
• “electron”
•
• Thomson:
calculated
charge:mass
ratio of e-
- charge
• in
all matter
• Also
detected + rays,
which lead to
discovery of protons
_
cathode
+
anode
dwb.unl.edu/.../demos/jpeg/cath7.jpg
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• Oil
matter is composed of tiny indivisible particles called
atoms
• All
atoms of one element are exactly alike, but atoms of
different elements are different from each other
• Atoms
are neither created or destroyed in any chemical
reaction & Compounds always have the same ratio of
elements
ELECTRONS
Millikan
• American
• All
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ELECTRONS
• Robert
DALTON’S
POSTULATES
Which
parts of Dalton’s
theory was proven
incorrect…
- 1909
drop experiments
www-news.uchicago.edu
• Discovered
www-news.uchicago.edu
that e- had a -1 charge
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http://people.clarkson.edu/~ekatz/scientists/millikan_scheme2.jpg
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AS OF 1900…
ELECTRONS
• Thomson
• Plum
Pudding Model (Cookie-dough)
• Nagaoka
www-news.uchicago.edu
• Japan
~ same time as Rutherford
that e- travel around the
nucleus like planets
• Proposed
http://people.clarkson.edu/~ekatz/scientists/millikan_scheme2.jpg
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THE NUCLEUS
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GOLD FOIL EXPERIMENT
• Lord
Rutherford, English,
1912-1913
• Gold
Foil Experiments
• Atom
was mostly empty space
w/ solid, dense, + charged
center (nucleus)
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THE NUCLEUS
• Lord
Rutherford, English,
• Proved NUCLEAR/Planetary
MODEL OF THE ATOM
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GOLD FOIL EXPERIMENT
• Thomson
NEUTRONS
• discovered
that 3 types of Ne atoms
existed (3 different masses)
• Isotopes
• In
order to explain the different masses of
isotopes, scientist now believed there must be a
3rd particle (later called neutrons).
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DALTON’S
POSTULATES
Which
parts of Dalton’s
theory was proven
incorrect…
• All
matter is composed of tiny indivisible particles called
atoms
• All
atoms of one element are exactly alike, but atoms of
different elements are different from each other
• Atoms
are neither created or destroyed in any chemical
reaction & Compounds always have the same ratio of
elements
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