Ips Ch. 18

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Ips Ch. 18

  1. 1. Chapter 18: Atomic Models 18.1 – Models Help Us Visualize the Invisible World of Atoms
  2. 2. 18.1 Models Help Us Visualize the Invisible World of Atoms <ul><li>We cannot see atoms directly, but we can generate images of them indirectly. </li></ul><ul><li>Scanning Tunneling Microscope (STM) – Produces images by dragging a needle back and forth over the surface of a sample. </li></ul>
  3. 3. 18.1 Models Help Us Visualize the Invisible World of Atoms <ul><li>An STM is also used to push atoms into desired positions. </li></ul><ul><li>The STM opened up the field of nanotechnology. </li></ul><ul><li>Nanotechnology – Building incredibly small circuits and motors atom by atom. </li></ul>
  4. 4. 18.1 Models Help Us Visualize the Invisible World of Atoms <ul><li>Physical model – A representation of a very large or small object shown at a convenient scale. </li></ul><ul><li>Conceptual Model – An explanation that treats what is being explained as a system. </li></ul>
  5. 5. 18.1 Models Help Us Visualize the Invisible World of Atoms <ul><li>System – The interactions among component parts matter most. </li></ul><ul><li>An STM can only show the positions of atoms and not actual images! </li></ul>
  6. 6. 18.2 – Atoms Can Be Identified by the Light They Emit
  7. 7. 18.2 – Atoms Can Be Identified by the Light They Emit <ul><li>An atom emits light when it loses energy. </li></ul><ul><li>Each element produces its own distinctive glow. </li></ul><ul><li>White light is separated into its color components by a prism. </li></ul><ul><li>Spectroscope – Instrument used to observe the color components of any light source. </li></ul>
  8. 8. 18.2 – Atoms Can Be Identified by the Light They Emit <ul><li>Atomic Spectrum – The pattern of frequencies formed by a given element. </li></ul>
  9. 9. 18.3 Niels Bohr Used the Quantum Hypothesis to Explain Atomic Spectra <ul><li>Light travels as a wave, but strikes as a particle. </li></ul><ul><li>Quantum Hypothesis – States that a beam of light is a stream of zillions of discrete particles. </li></ul><ul><li>Photon – A particle of light. </li></ul><ul><li>Quantum – The smallest unit of something. </li></ul>
  10. 10. 18.3 – Niels Bohr Used the Quantum Hypothesis to Explain Atomic Spectra <ul><li>Bohr said that potential energy of an electron in an atom depends on the electron’s distance from the nucleus. </li></ul><ul><li>The more energy added, the more the electron moves away from the nucleus. </li></ul><ul><li>Bohr concluded there must be a number of distinct energy levels. </li></ul>
  11. 11. 18.3 – Niels Bohr Used the Quantum Hypothesis to Explain Atomic Spectra <ul><li>Bohr gave each energy level a principal quantum number n , where n is always some integer. </li></ul><ul><li>Bohr’s model of the atom is known as the Planetary model . </li></ul>

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