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Used in Mr. Backlund's Physical Science class for Chapter 4.

Used in Mr. Backlund's Physical Science class for Chapter 4.

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  • 1. Atomic Structure Timeline
    • Scientific models- a theory, description, or explanation based on known facts and observable behaviors
    • Good models
      • Based on observation
      • Can successfully make predictions
      • Is changeable as new info. becomes available
  • 2. Alchemy (next 2000 years)
    • Mixture of science and mysticism.
    • Lab procedures were developed, but alchemists did not perform controlled experiments like true scientists.
  • 3. Democritus (500 B.C.)
    • Proposed that matter was composed of tiny indivisible particles
    • Not based on experimental data
    • Greek: atomos “indivisible”
  • 4. John Dalton (1803)
    • British Schoolteacher
      • based his theory on others’ experimental data
      • Interest was in meteorology
    • Billiard Ball Model
      • atom is a uniform, solid sphere
  • 5. John Dalton Dalton’s Four Ideas 1. Elements are composed of small indivisible particles called atoms. 2. Atoms of the same element are identical. Atoms of different elements are different. 3. Atoms of different elements combine together in simple proportions to create a compound. 4. In a chemical reaction, atoms are rearranged, but not changed.
  • 6. J. J. Thomson (1897)
    • Cathode Ray Tube Experiments
      • beam of negative particles
    • Discovered Electrons
      • negative particles within the atom
    • Plum-pudding Model
  • 7. J. J. Thomson (1897)
    • Plum-pudding Model
      • positive sphere (pudding) with negative electrons (plums) dispersed throughout
      • Atoms are neutral-no charge
  • 8. Ernest Rutherford (1910)
    • Gold Foil Experiment
    • Discovered the nucleus
      • dense, positive charge in the center of the atom
      • Electrons scattered around nucleus
      • Atoms are mostly empty space
  • 9. Ernest Rutherford (1910)
    • Nuclear Model
      • dense, positive nucleus surrounded by negative electrons
  • 10. Niels Bohr (1913)
    • Bright-Line Spectrum
      • tried to explain presence of specific colors in hydrogen’s spectrum
    • Energy Levels
      • electrons can only exist in specific energy states
    • Planetary Model
  • 11. Niels Bohr (1913)
    • Planetary Model
      • electrons move in circular orbits within specific energy levels (orbits)
    Bright-line spectrum
  • 12. Erwin Schrödinger (1926)
    • Quantum mechanics
      • electrons can only exist in specified energy states
    • Electron cloud model
      • orbital : region around the nucleus where e - are likely to be found
  • 13. Erwin Schrödinger (1926)
    • Electron Cloud Model (orbital)
    • dots represent probability of finding an e - not actual electrons
  • 14. Electron Cloud Model
    • Electrons not in definite path, but in a probable location
    • Location based on energy of electron
    • Atom is a small, + charged nucleus surrounded by a region of electrons
    • # of protons and electrons are equal in a neutral atom
  • 15. Conclusion
    • All updates were based on evidence
    • Proceeded rapidly from 1800 to the present