| MadSci Network: Chemistry |
Dear Ashley, While many techniques that can prove that atoms exist, and a few kinds of microscopes can almost see atoms, the easiest way to "see" an atom is to use the Scanning Tunneling Microscope (STM). An STM works differently from the light microscopes you might see in biology class. The sample must be very flat, clean, and able to conduct electricity. A super-sharp needle is held a short distance (just a few times the width of an atom) over the sample. At this distance, electrons can jump across the gap between the needle and the surface, in a process called tunneling. The rate at which they jump is very sensitive to the width of the gap. The needle is scanned back and forth over the surface in a regular pattern. When the needle goes over an atom, the height of the atom changes the gap width and makes a big change in the rate of tunneling. A computer controls the scanning and makes a map of how much tunneling occurs at each point. You never directly see the atoms, as you would see cells in a light microscope. Instead you "see" them indirectly, as features in a map or picture made by the computer. The STM was invented by Dr. Gerd Binnig and Dr. Heinrich Rohrer in 1981 at IBM Zurich. They "saw" atoms on a silicon surface by the end of 1982. They won the 1986 Nobel Prize for physics for their work. Some web sites of interest include... IBM's "Art Gallery" of pictures of atoms Some images from the Technical University at Vienna A simple explanation of STM A more detailed explanation. You could also page through the Web links at the Vienna site. Happy hunting! Deron Walters Rice University
Try the links in the MadSci Library for more information on Chemistry.