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Quantum Numbers

Determining the location of an electron within an atom.

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Where Did I Put That Electron?

Where Did I Put That Electron?

Credit: George William Clarkson Kaye
Source: http://en.wikipedia.org/wiki/File:Cosser_Crookes_xray_tube.jpg
License: CC BY-NC 3.0

The Crooke’s tube was the first device that allowed us to get a look at that elusive particle, the electron. High voltage current was passed from one end of the tube to the other. Material in the tube would fluoresce when excited by electrons, so we could see the path of the electron beam. The electrons themselves were invisible, but the tube gave strong evidence of their presence and properties.

Why It Matters

  • The Global Positioning System (GPS) provides invaluable information about your location and direction of travel. Inexpensive systems can be purchased separately or an app can be downloaded on your smartphone. Many cars now come equipped with GPS as a standard add-on. The navigation system on your phone will locate destinations for you and provide driving directions (however, the voice giving you the directions seems to sound very annoyed when you don’t follow those directions completely). A commercial GPS system currently has a “worst-case” accuracy of about 7-8 meters, while many more expensive models can provide better than 3-meter accuracy.
  • Credit: Daveynin
    Source: http://www.flickr.com/photos/daveynin/6067262367/
    License: CC BY-NC 3.0

    GPS can also be used for hiking and other outdoor activities [Figure2]

  • A GPS signal bounces off the earth and has absolutely no effect on the motion of our planet. However, when we try to look at electrons, we have a much bigger challenge. Anything we use to look at the electron disturbs the motion of that particle. So when we talk about the location of an electron, we can only say that it is somewhere within a certain region of space. In the same way, orbitals for specific electrons do not pin-point that electron’s location, but just gives an idea that the electron might be some place in that region. But some aspects of quantum mechanics also suggest that it might not even exist at a given moment in time.
  • The research published to date does not take a snapshot of an electron so we can see what it looks like. What we have been able to measure so far is the effect of the electron on its surroundings. We can stimulate an electron with a variety of devices and see what happens in the area around the electron. Since there is no system at present small enough to truly interact with an electron and stop it, we’ll just have to rely on what the electron does to the environment around it.
  • Watch a video at the link below to see a moving electron:


Show What You Know

Use the links below to learn more about electrons. Then answer the following questions.

  1. How accurate are GPS set-ups that have an augmentation system?
  2. Did the attosecond absorption spectroscopy experiment actually see electrons?
  3. What did the atomic force microscope experiment show?
  4. What puzzling conclusion did these workers come to?

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    Image Attributions

    1. [1]^ Credit: George William Clarkson Kaye; Source: http://en.wikipedia.org/wiki/File:Cosser_Crookes_xray_tube.jpg; License: CC BY-NC 3.0
    2. [2]^ Credit: Daveynin; Source: http://www.flickr.com/photos/daveynin/6067262367/; License: CC BY-NC 3.0

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