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Thomson's Atomic Model

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Seeing with Electrons

Seeing with Electrons

Credit: Luisa Howard
Source: http://commons.wikimedia.org/wiki/File:Insect_SEM_gracilariidae.jpg
License: CC BY-NC 3.0

Eek! What is this? Is it a creature from a horror movie? Actually, it’s a greatly magnified image of a moth’s head!

Why It Matters

  • The moth image above would not have been possible without the discovery of the electron. The image was made using an electron microscope.
  • An electron microscope uses electrons, rather than light, to make magnified images of objects. It allows us to see things that are much, much smaller than those we can see with a light microscope.
  • Credit: Dave Pape
    Source: http://www.flickr.com/photos/dpape/4057923705/
    License: CC BY-NC 3.0

    A electron microscope station [Figure2]

     

  • The electron microscope was invented in the early 1930s, just a few decades after electrons were discovered. That landmark discovery was made by British scientist J.J. Thomson in 1897. Watch this video to learn how Thomson discovered the electron and how he modeled its place in the atom:

http://www.dnatube.com/video/1816/The-Discovery-of-the-Electron-2-of-15

Show What You Know

At the links below, learn more about electrons and electron microscopes. Then answer the questions that follow.

  1. Thomson’s discovery of the electron was the first discovery of a particle smaller than the atom. How did Thomson model the place of electrons inside atoms?
  2. Thomson’s discovery of the electron was monumental, but his model of the atom was incorrect. We now know that electrons are found in the largely empty space around the tiny positive nucleus of the atom. This allows electrons to be involved in chemical bonds and electricity. Explain the role of electrons in these two areas.
  3. Contrast electron microscopes with light microscopes.
  4. Describe in general how an electron microscope works.
  5. The earliest electron microscopes were transmission electron microscopes. Later, scanning electron microscopes were invented. How do these two types of electron microscopes differ?

Image Attributions

  1. [1]^ Credit: Luisa Howard; Source: http://commons.wikimedia.org/wiki/File:Insect_SEM_gracilariidae.jpg; License: CC BY-NC 3.0
  2. [2]^ Credit: Dave Pape; Source: http://www.flickr.com/photos/dpape/4057923705/; License: CC BY-NC 3.0

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