UP AND ATOM

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UP AND ATOM

• Its time for

THE HISTORY OF THE ATOM !
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Democritus (400 B.C.)

• First person to propose that matter is made of
  about 100 tiny particles called atoms that
  collide and combine to make everything.
• His theory was not widely believed, even though
  it turned out to be correct.
• Like other scientists of his time, he had no real
  evidence for his ideas.

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Aristotle -- 350 B.C.

• Denied the existence of atoms.
• Said matter consisted of combinations of only
  four elements -- air, earth, fire, and water.
• Was widely respected, and his ideas formed the
  basis of science for nearly 2000 years.
• Lead to alchemy and superstition.

FIRE
AIR
WATER
EARTH
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400 B.C. - 1600 A.D. The Dark Ages of Chemistry
The idea of atoms was lost
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Robert Boyle 1661
Renews belief in the idea of atoms
through his experiments with gases
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Antoine Lavosier1780
Modern Chemistry

• Father of
• Modern Chemistry

Antoine

• Developed the theory of
• Conservation of Matter

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John Dalton --1800(a.k.a the marble guy)

• Atoms are all solid with uniform density
• Atoms are the smallest particles of nature
• All atoms of the same element are identical
• Atoms of different sizes can combine to form
  compounds

An atom (Close-up view)
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1879William Crookes

• Discovers a negatively charged beam in an
  electrified vacuum tube.

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• Proved that Crookes negative beam was really
  particles he called electrons.
• Realized that these electrons must be smaller
  than the atom
• Developed the Plum Pudding model of the atom
• First person to realize that atoms are made of
  small parts

J.J. Thomson
1897
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What is plum pudding?
I prefer mint chocolate Chip ice cream
Atoms are negative electrons stuck in a positive
glob
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Ernest Rutherford - 1911

• Performed Gold Foil Experiment
• Won Nobel Prize for Chemistry

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The Gold Foil Experiment

• Bombard thin piece of gold foil with alpha
  particles
• Result a few are deflected while most are
  unaffected
• What does it all mean?

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What Happened?
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What Does it Mean?

• Atoms have dense area in the middle
• The nucleus
• The proton
• Electrons travel around away from the nucleus
• The atom is mostly empty space

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NIELS BOHR 1913

• Was a friend of Einstein
• Developed important ideas of quantum physics and
  atomic structure
• Use light spectrum to explain the structure of
  the atom

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Light Spectrum
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Niels Bohr

• Compares electrons orbiting the nucleus of an
  atom to planets orbiting around the sun.
• Electrons occupy distinct orbitals.
• Orbitals have certain energies and distances from
  the nucleus.

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Erwin Schrodinger

• Regions where electrons are most likely found are
  called electron clouds.
• Different types of orbitals have different shapes
  and different levels of energy.
• Although difficult to understand, the results
  were spectacular!
• This new model of the atom explained the physical
  properties of atoms, and the Periodic Table,
  perfectly.

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James Chadwick1932

• Discovered the neutron

neutron

• Predicted by Rutherford in1920, but very
  difficult to detect.
• New tool for probing and changing the nucleus of
  an atom.

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1980s

• The first atoms are seen with scanning
  tunneling microscopes

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1995

• Fermi lab scientists in Batavia,
• Illinois study and detect six types
• Of quarks
• Quarks are particles believed to
• Make up protons and neutrons