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Historical Models

Historical Models. Science Starter. 20. Which of these best describes the particle motion taking place as gas is exposed to freezing temperatures? A) The particles decrease in speed. B) The particles move with more force. C) The motion of the particles becomes random.

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Historical Models

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  1. Historical Models

  2. Science Starter • 20. Which of these best describes the particle motion taking place as gas is exposed to freezing temperatures? • A) The particles decrease in speed. • B) The particles move with more force. • C) The motion of the particles becomes random. • D) The motion of the particles is unchanged. • 21. Which of these substances is an element? • F) Steel • G) Chlorine • H) Plastic • J) Sugar

  3. Draw a chart in your lab notebook

  4. John Dalton’s Atomic Theory • All matter is made up of individual particles called atoms, which cannot be divided. • All elements are composed of atoms. • All atoms of the same element have the same mass, and atoms of different elements have different masses. • Compounds contain atoms of more than one element. • In a particular compound, atoms of different elements always combine in the same way.

  5. What is a model? • A representation of something • Ex. The tennis balls of science • What do they represent? • Are they actually what they represent? • Usually a simplified version of something complex

  6. Dalton’s Atomic Model • Small • Solid • Spherical • Indivisible

  7. JJ Thomson’s Plum Pudding Model • Positive and Negative Charges are dispersed throughout the atom • Atoms have charge • Electrons are stuck in the atom like raisins are stuck in a bowl of plum pudding

  8. JJ, Plum Pudding, Chocolate Chip

  9. Ernest Rutherford • In 1906 he decided to test the plum pudding model. • He shot alpha particles at gold foil. • Some passed through the “empty” space outside the nucleus • Some bounced off the nucleus of the atom and back at the screen

  10. Peach Pit Model (Rutherford) • Dense, positively charged nucleus • Empty space for most of atom

  11. Bohr Model • Dense nucleus • Electrons are found in distinct energy levels that are only found a specific distance from the nucleus

  12. Modern Atomic Model • Dense nucleus • Space outside nucleus where electrons are most likely to be found • Do NOT follow fixed paths like in the Bohr Model • “Fan” Model

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