Atomic theory  gr 9 -may 24
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atomic molecular theory notes May 24

atomic molecular theory notes May 24

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Atomic theory gr 9 -may 24 Presentation Transcript

  • 1. ATOMIC THEORY Lewis
  • 2. 1700’s
    • • In the 1700’s scientist agreed that elements could not be broken down.
    • • 30 +/- elements identified or known
    • • Belief that elements could be mixed together to form compounds
  • 3. 1808 - John Dalton
    • • Dalton proposed an Atomic Theory
    • to explain chemical reactions.
    • • He envisioned the ATOM .
    • * smallest particles of an element
    • * smooth solid sphere
    • * no electrical charge
    • • there was a belief that atoms and molecules were thought to be the same until Dalton.
    • • Scientists now believed that 2 or more
    • Non-Metalic atoms could be combined to form compounds.
  • 4. 1808 - John Dalton Theory
    • • All matter was made of ATOMS - these were to small to see.
    • • Each element has its own kind of Atom with its own mass.
    • • All Atoms of a single type of element are identical.
    • • Compounds are created when atoms of different elements combine in a specific ratio.
    • • Atoms can not be created, destroyed, or subdivided during a chemical change
  • 5. In the 1800’s
    • • until Dalton’s work many scientists believed that molecules and atoms were the same.
    • • after Dalton it was accepted that a molecule was the combination of two or more non-metal atoms in combination.
    • • in 1830 Michael Faraday showed atoms
    • can gain electrical charges.
    • (static electricity)
  • 6. Michael Faraday
    • added the following to ATOMIC THEORY
    • • matter must contain positive (+) and negative (-) charges.
    • • opposite charges attract & like repel
    • • atoms combine to form the particles of a compound because of the electrical attraction between the charges atoms ( Ions ).
  • 7. 1898 - J.J. Thomson
    • • discovered the presence of smaller particles than the atom… the negatively charged ELECTRON,
    • • he proposed than the atom is mostly positively charged matter with small negatively charged electrons scattered randomly throughout.
    • The Plum Pudding Model
    • ( or the chocolate cookie )
  • 8. Thomson’s revisions to Atomic theory
    • • Atoms contain electrons.
    • • electrons have a negative charge and a very small mass.
    • • the rest of the Atom is positively charged.
    • • electrons can be added and removed.
    • ( ie. Rubbing a balloon against cloth )
  • 9. Ernest Rutherford - 1911 the Canadian connection
    • While at the University of McGill, Quebec, Rutherford shot alpha particles at gold foil and found that most went straight through.
    • He reasoned that most of the mass and the positive particles were at the centre of the atom… he called this the nucleus.
  • 10. Ernest Rutherford Rutherford amended the Atomic Theory to include the following.
    • • the Nucleus contains all of the positive charges and most of the mass.
    • • the Nucleus contains positively charged Protons and uncharged Neutrons.
    • • Neutrons have some mass, Protons have more.
    • • the Nucleus is very small.
    • • Electrons orbit the nucleus like satellites.
    • • the mass of an electron is 1/1800 of the protons.
    • • the size of an atom is determined by the size of orbit of electrons.
    • • there is empty space between the nucleus and the electrons.
  • 11.
    • • When Rutherford published his findings in 1912, he knew that his version of the ATOMIC THEORY already had errors and would need to be revised.
    Modern Atomic Theory
  • 12.