Atomic Structure

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Atomic Structure
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What is an Atom?

• The smallest part of an element.

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Early models of the atom
ITS ALL GREEK TO ME...

• Democritus
• Matter is
• made of tiny indivisible and indestructible
  particles called atoms.

460-370 BC
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John Dalton - 1803

• Atom is indivisible.
• All atoms of a given element are identical.
• Conservation of atoms in a chemical reaction.

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ALL MATTER IS COMPOSED OF EXTREMELY SMALL PARTICLES CALLED ATOMS
ATOMS OF A GIVEN ELEMENT ARE IDENTICAL IN SIZE, MASS, AND OTHER PROPERTIES ATOMS OF DIFFERENT ELEMENTS DIFFER IN SIZE, MASS, OTHER PROPERTIES
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ATOMS CAN NOT BE CREATED OR DESTROYED
ATOMS OF DIFFERENT ELEMENTS COMBINE IN SIMPLE WHOLE RATIOS TO FORM CHEMICAL COMPDS.
IN CHEMICAL REACTIONS, ATOMS ARE COMBINED, SEPARATED, OR REARRANGED


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Static Electricity

• 1750s Ben Franklin studied charges.
• Two types Positive and Negative

Static Electricity Commercial
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• THE FIRST DISCOVERY OF A SUBATOMIC PARTICLE
  RESULTED FROM THE INVESTIGATIONS INTO THE
  RELATIONSHIP BETWEEN ELECTRICITY AND MATTER.
• IN THE LATE 1800S, MANY EXPERIMENTS WERE
  PERFORMED IN WHICH ELECTRIC CURRENT WAS PASSED
  THROUGH VARIOUS GASES AT LOW PRESSURE.
• CARRIED OUT IN
  TUBES CALLED
  CATHODE-RAY TUBES

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• INVESTIGATORS NOTICED THAT WHEN CURRENT WAS
  PASSED THROUGH A CATHODE RAY TUBE, THE SURFACE OF
  THE TUBE DIRECTLY OPPOSITE THE CATHODE GLOWED.

Cathode Ray Video
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J.J. Thomson 1856-1940
I PLAY WITH ELECTRONS
THOMPSON CONCLUDED THAT ALL CATHODE RAYS ARE
COMPOSED OF IDENTICAL NEGATIVELY CHARGED
PARTICLES LATER WERE CALLED ELECTRONS.
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J.J. Thomson

• Discovered electron
• Plum Pudding Model

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Ernest Rutherford - 1909
HOW IS THE ATOM BUILT?
Gold Foil Experiment
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Ernest Rutherford

• Gold Foil Experiment
• Dense () charge nucleus
• Electrons orbiting on outside
• Atom is mostly
• empty space