Scale Drawings of Atoms and Orbitals: Rubidium Through Xenon

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

Although almost any chemical reference will have data on ionic radii and electron configuration, and tabulations of energy levels are not hard to find, there is little readily available data on the relative sizes of orbitals. Ionic radii are useful in crystal modeling, electron configuration and energy levels for all kinds of stuff, but sizes of orbitals don't seem to have much practical use.

It's impossible to measure the sizes of orbitals and even of atoms directly. You measure macroscopic objects basically by bouncing light off them (say off the object and a ruler) but wavelengths tiny enough to show atomic structure in detail (nanometers and less) are energetic enough to destroy what you want to see. Ionic radii are calculated from atomic spacings in materials. Orbital radii principally come out of theories whose main purpose is to account successfully for the other properties of atoms. These drawings are based on data from J. T. Waber and D. T. Cromer, Orbital Radii of Atoms and Ions, Journal of Chemical Physics, 15 June, 1965, vol. 42, no. 12, p. 4116-4123. The sizes shown are the radii of the maximum electron density, so the actual extent of significant electron density is maybe 50% larger.

All the drawings are to common scale. For orbitals with lobes, the principal lobes are shown but there is no attempt to portray the complex inner structure. It gets plenty busy in toward the center of the atom anyway.