The Department of Chemistry invites you to its departmental seminar on Monday, April 13, at 4:10 p.m. in Fulmer Hall, room 438.
Dr. Thom H. Dunning from Pacific Northwest National Laboratory and the University of Washington will present, Insights into the “First Row Anomaly” from Generalized Valence Bond Theory.
Abstract: The chemical properties of the elements in the first row of the Periodic Table, lithium–neon, are significantly different than those of the other elements in the same group. One manifestation of this “First Row Anomaly” is the existence of SF4 and SF6, whereas OF4 and OF6 are unstable. Both molecular orbital (MO) and valence bond (VB) theories provide only a weak explanation for the anomaly. However, a simple extension of VB theory, Generalized Valence Bond (GVB) theory, provides a simple, straightforward explanation of the “First Row Anomaly” and shows how the underlying cause of the hypervalency of the elements beyond the first row explains many other manifestations of the “Anomaly.” The GVB wave function is more accurate than the Hartree-Fock wavefunction, including both atomic and molecular non-dynamical correlation effects, but, unlike wavefunctions with multiple spatial configurations, the GVB wave function can be interpreted using concepts familiar to most chemists. We will discuss a number of examples that illustrate the power of GVB theory to explain the “First Row Anomaly”: the nature of the bonding in hypervalent molecules such as SF4, the relative energies of the isomers of F(NX) with X = (O,S), the transition states for inversion in FnNH(3-n) and FnPH(3-n), and, in a nod to aberrations in the first row, the nature of the bonding in C2.
Contact: Chelsea (Pickett) Gao, chelsea.m.pickett@wsu.edu.
