Development Of Atomic Theory<br />Physical Science<br />Chapter 4.1<br />
Objectives<br />Describesome of the experiments that led to the current atomic theory.<br />Compare the different models o...
The Beginning of the Atomic Theory<br />440 BCE, a Greek philosopher, Democritus<br />thought that you would eventually en...
Dalton’s Atomic Theory<br />Published in1803. Stated that<br />All substances are made of atoms.<br />Atoms are small part...
Thomson’s Discovery of Electrons <br />Negatively Charged Particles<br />Used cathode-ray tube <br />Discovered negatively...
Rutherford’s Atomic “Shooting Gallery”<br />Negatively Charged Particles<br />1909<br />Ernest Rutherford aimed a beam of ...
Rutherford’s Model of atom<br />
Where are the electrons?<br />Far from the Nucleus<br />Rutherford proposed that in the center of the atom is a tiny, posi...
Size of the Nucleus<br />
Modern Atomic Theory<br />The Modern Atomic Theory<br />Regions inside the atom where electrons are likely to found<br />T...
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Physical science 4.1 : Development of Atomic Theory

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Physical science 4.1 : Development of Atomic Theory

  1. 1. Development Of Atomic Theory<br />Physical Science<br />Chapter 4.1<br />
  2. 2. Objectives<br />Describesome of the experiments that led to the current atomic theory.<br />Compare the different models of the atom.<br />Explain how the atomic theory has changed as scientists have discovered new information about the atom.<br />Bellringer<br />The following is a quote by Democritus (c. 460–c. 370 bce). <br />“Color exists by convention, sweet by convention, bitter by convention; in reality nothing exists but atoms and the void.”<br />What do you know about Democritus? And why are his thoughts important?<br />
  3. 3. The Beginning of the Atomic Theory<br />440 BCE, a Greek philosopher, Democritus<br />thought that you would eventually end up with a particle that could not be cut. <br />He called this particle an atom.<br />Aristotle, another Greek philosopher, <br />disagreed with Democritus<br />He believed that you would never end up with a particle that could not be cut.<br />atom<br />smallest particle into which an element can be divided and still be the same substance.<br />
  4. 4. Dalton’s Atomic Theory<br />Published in1803. Stated that<br />All substances are made of atoms.<br />Atoms are small particles that cannot be created, divided, or destroyed.<br />Atoms of the same element are exactly alike<br />Atoms of different elements are different. <br />Atoms join with other atoms to make new substances.<br />Not Quite Correct <br />The atomic theory was then changed to describe the atom more correctly.<br />
  5. 5. Thomson’s Discovery of Electrons <br />Negatively Charged Particles<br />Used cathode-ray tube <br />Discovered negatively charged particles<br />electrons.<br />Plum – Pudding model<br />New model of the atom. <br />Electrons were mixed throughout an atom, like plums in a pudding.<br />
  6. 6.
  7. 7. Rutherford’s Atomic “Shooting Gallery”<br />Negatively Charged Particles<br />1909<br />Ernest Rutherford aimed a beam of small, positively charged particles at a thin sheet of gold foil. <br />Surprising Results<br />Expected the particles to pass right through the gold in a straight line. <br />Surprise, some of the particles were deflected!!<br />
  8. 8. Rutherford’s Model of atom<br />
  9. 9. Where are the electrons?<br />Far from the Nucleus<br />Rutherford proposed that in the center of the atom is a tiny, positively charged part<br />called the nucleus<br />Nucleus is 100,000 times smaller than atom<br />Bohr’s Electron Levels<br />1913<br />NielsBohr proposed that electrons move <br /> around the nucleus in certain paths, or <br /> energy levels<br />
  10. 10. Size of the Nucleus<br />
  11. 11. Modern Atomic Theory<br />The Modern Atomic Theory<br />Regions inside the atom where electrons are likely to found<br />These regions are called electron clouds<br />

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