Atoms may repel or attract each other, but bound systems get virtually all of the attention in the classroom. To address the imbalance, instructors can explore the basis of repulsion in a few simple systems and highlight the important role played by the Pauli principle. A good example is the first triplet excited state of H[subscript 2] wherein…

In multielectron atoms or molecules, quantized electronic energy states known as term states provide a framework for interpreting absorption and emission spectra. Enumerating the term states associated with any particular electron configuration is possible using time-honored procedures, but the underpinnings of the methods do not always receive…

Students collect magnetic susceptibility data to verify that Hund's rule correctly predicts electronic configurations. Systems examined include three commercially available lanthanide(III)-containing complexes of the form M(acac)[subscript 3](H[subscript 2]O)[subscript 2] (where M = La(III), Nd(III), and Gd(III), and acac denotes the [CH[subscript…

Electronic spectra often exhibit vibronic structure when vibrational and electronic transitions occur in concert. Theory reveals (1) that orbital symmetry considerations determine specific roles played by the nuclear degrees of freedom and (2) that the vibrational excitation is often highly regiospecific, that is, attributable to an identifiable…

Discusses how a metal ion is bound to a particular enzyme, focusing the blue copper centers found in a variety of organisms. Coordination geometry of the blue copper site, donor set, direct structural studies, and single-crystal spectroscopy are the major topic headings. (JN)