The Atomic Theory

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The Atomic Theory
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Atom

• The smallest particle into which an element can
  be divided and still be the same substance.
• The smallest particle of an element that retains
  the properties of that element.

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The Atom
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Protons and Neutrons
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Atomic Theory

• The existence of atoms is not a new idea.
• Atomic theory has been around for more than
  2,000 years.
• A theory is a unifying explanation for a broad
  range of hypotheses and observations that have
  been supported by testing.

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John Dalton

• All substances are made of atoms.
• Atoms are small particles that cannot be created,
  divided, or destroyed.
• Atoms of the same element are exactly alike, and
  atoms of different elements are different.
• Atoms join with other atoms to make new
  substances.

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J.J. Thomson

• Thomson discovered that there are small particles
  inside the atom.
• Therefore, atoms can be divided into even smaller
  parts.
• Thomsons model became known as Plum Pudding
• JJ Thomson is credited with discovering
  ELECTRONS

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Ernest Rutherford

• Rutherford proposed that in the center of the
  atom is a tiny, extremely dense, positively
  charged region called the NUCLEUS.

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Rutherfords Model
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James Chadwick

• The Neutron, one of the particles in the
  Nucleus of an Atom, is discovered by British
  physicist James Chadwick.

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Niels Bohr

• Bohr suggested that electrons traveled around the
  nucleus in definite paths.
• Bohr proposed the Planetary path version.
• He proposed that no paths are located between the
  levels, but electrons can jump from a path in one
  level to a path in another level.
• A very good example of this would be a ladder.

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Bohrs Model
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The Modern Theory

• According to the current theory, electrons do
  not travel in definite paths as Bohr suggested.
• In fact their paths can not be predicted.
• Regions inside the atom where electrons are
  likely to be found are called ELECTRON CLOUDS.

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The Modern Theory