Download Chap 11 Sect 1 Notes Atomic Theory

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ATOMIC THEORY
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Democritus Atom
 He
was said to be the first step
toward the current atomic
theory.
 Hypothesized

all matter is composed of tiny
particles made of a single
material
 Claimed
atoms are always
moving
 Form new substances by
joining together
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 According
forever.
to him, atoms cannot be divided
 The
object will become so small and invisible
that you cannot divide it any further.
 He
said that these indivisible, invisible
particles are ATOMS. The word atom means
“uncuttable”.
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Aristotle
Believed
there was “no smallest part
of matter”
Substances
were made up of fire, air,
earth, and water
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John Dalton
He
is best known for his
work in the development of
modern atomic theory.
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5 POINTS of
Dalton’s Theory
 All
matter consists of tiny particles called
atoms. Atoms cannot be created, divided,
or destroyed.
 All atoms of a given element are identical in
mass and properties.
 The atoms of a given element are different
from those of any other element.
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 Compounds
are formed by a
combination of two or more different
kinds of atoms.
 Compounds
are pure substances. They can’t be
separated into elements by phase changes
because the atoms of different elements are
bonded to one another and are not easily
separated from one another.

A chemical reaction results in a
rearrangement of atoms.
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J. J. Thomson
 Discovered
of electron
 Discovered
of isotopes
 Proposed
Model
the Plum Pudding
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Thomson’s Cathode-Ray Tube
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PLUM PUDDING
MODEL
•Also known as the “Chocolate Chip
Cookie or Blueberry Muffin Model.”
•Atom is composed of electrons
surrounded by a “soup” of positive
charge to balance the electron’s
negative charge, like negativelycharged “plums” surrounded by
positively-charged “pudding”.
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•Sometimes visualized as having a cloud of
positive charge
•Electrons were free to rotate within the cloud
of positive substance.
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Ernest Rutherford
•Discovered that atoms have
their positive charge
concentrated in a very small
nucleus.
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Gold Foil
Experiment
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•The results of the experiment
demonstrated the existence of the
atomic nucleus.
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Large
amount of the atom’s mass
is concentrated into a very small
core.
Outside
of this “central charge”, he
proposed that the atom was
mostly empty space.
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Bohr’s Model
 also
known as the
planetary model
 neutrons
and protons are
in the nucleus while the
electrons are orbiting the
nucleus
 electrons
are able to jump
from one orbit to another
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Electron Cloud
Model
 consists
of a dense nucleus composed of
protons and neutrons surrounded by
electrons that exist in different clouds at the
various energy levels.
 Erwin
Schrodinger and Werner Heisenburg
explained where the electrons would most
likely be found in the regions or clouds.