Matter is Made up of Atoms

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Matter is Made up of Atoms
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The Beginning

• Democritus
• Proposed that matter is made up empty space and
  tiny particles called atoms
• Lavoisier
• Mass of reactants in the container before a
  chemical reaction is equal to the mass of the
  products after the reaction (aka Law of
  Conservation of Matter)

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• Proust
• Elements that composed the compounds are always
  in a certain proportion of mass (aka Law of
  Definite Proportions)
• Dalton
• Atomic Theory
• All matter is made up of atoms.
• Atoms are indestructible and cannot be divided
  into smaller particles.
• All atoms of one element are exactly alike, but
  they are different from atoms of other elements.

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Atomic Structure Scientists

• Dalton
• Thought the atom was a small solid ball
• Thompson
• Discovered the electron
• Experiment Cathode-Ray Tube
• Rutherford
• Discovered the nucleus
• Experiment Gold-Foil Experiment

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JJ Thompson
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Rutherford
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Thompsons Plum Pudding Model
Rutherfords results when alpha particles where
beamed through foil
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• Millikan
• Discovered the quantity of charge carried by an
  electron (using Thompsons work)
• Experiment Oil Drop

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Last but not least

• Bohr
• Discovered electrons occupy shells (energy
  levels)
• Explained that elemental properties are related
  to the occupancy of outermost electron shells
  (valence electrons)
• Showed that electrons can jump to higher shells
  with light absorption and fall back to lower
  shells with light emission

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Atomic Number and Masses

• Atomic Number the number of PROTONS in the
  nucleus of an atom of an element
• Also tells you the number of ELECTRONS since
  elements have no over all charge.
• The number of PROTONS determines the IDENTITY of
  the element
• Atomic Mass The sum of the PROTONS and NEUTRONS

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• Isotopes?
• Have different mass numbers because they have a
  different amount of NEUTRONS
• Because isotopes have a different number of
  NEUTRONS, they have also have a different mass
  number
• If they had a different amount of PROTONS, they
  would be a different element completely

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Sodium Isotopes
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• Example
• Neon- Atomic Number10
• Mass Number 20.180
• of Protons 10
• of Electrons 10
• of Neutrons 10

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Practice makes perfect
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Answers