Number 278 (Story #3), July 8, 1996 by Phillip F. Schewe and Ben Stein THE ELECTRICAL RESISTANCE OF A SINGLE XENON ATOM has been measured. One normally thinks of resistance as the characteristic of a huge number of atoms (in a wire). But by attaching one or two xenon atoms to the tip of a scanning tunneling microscope above a nickel surface, physicists at IBM have shown how conductivity can depend on the quantum state of individual atoms. The resistance of a one-atom "wire" was measured to be 10**5 ohms while that for two xenon atoms was 10**7 ohms. (Ali Yazdani, D.M. Eigler, and N.D. Lang, Science, 28 June 1996.)