![]() ![]() and ask the administrative assistant to place it in the mailbox of Cynthia Tompkins, faculty advisor. If you qualify and are interested in participating in the induction ceremony, please bring an unofficial transcript to the main office of the School of International Letters and Cultures (Durham Hall, 3rd Floor, SILC Main Office) between the hours of 9 a.m.–5 p.m. Also please note that the prerequisites for undergraduate students are distinct and much more detailed. Please note that there will be future induction ceremonies, at least one per year. If you are currently enrolled in your first two courses of your degree, you do not qualify at this time. You must have completed two courses towards your degree in the Spanish program. The student must rank in the upper 35% of their class - sophomore, junior or senior - and must have completed at least three semesters or five quarters of college work (institutions unable to generate class rank should use a 3.2 cumulative grade point average as this criterion).(The candidate MUST have earned grades in completed Spanish courses in order to qualify for membership.) The student must have a minimal grade point average of 3.0 on a 4.0 point scale in all Spanish courses taken.A student may be admitted to active membership while still enrolled in the second junior-level course if all other requirements have been met and if the instructor of the course certifies that the student’s work is of “B” or “A” quality. Each candidate must have completed three years of study of college-level Spanish (18 semester credit hours) or the equivalent thereof, including at least three semester hours of a course in Hispanic literature or Hispanic culture and civilization (Spanish for the professions may be considered as a Hispanic culture course provided that culture is the foundation of the course content) at the junior/3rd year level.For more information, please visit the organization's website. Outstanding students may also be nominated by their local chapters to receive prestigious awards recognizing noteworthy involvement in his/her local chapter. We will encounter these bonding situations in Chapter 5.Graduate student members may apply for research grants of up to $2000 to support research abroad. Transition metal complexes containing halide ligands can also have significant pπ-dπ bonding, in which a filled pπ orbital on the ligand donates electron density to an unfilled metal dπ orbital. The same kind of backbonding occurs with phosphine complexes, which have empty π orbitals, as shown at the right. The C-O infrared stretching frequency is diagnostic of the strength of the bond and can be used to estimate the degree to which electrons are transferred from the metal d-orbital to the CO π-antibonding orbital. This interaction strengthens the metal-carbon bond but weakens the carbon-oxygen bond. In metal carbonyl complexes such as Ni(CO) 4 and Mo(CO) 6, there is sideways overlap between filled metal d-orbitals and the empty π-antibonding orbitals (the LUMO) of the CO molecule, as shown in the figure below. Pπ-dπ bonding is also important in transition metal complexes. ![]() For example, phosphines (R 3P:) are good σ donors in complexes with transition metals, as shown below. Transition metal d-orbitals can also form σ bonds, typically with s-p hybrid orbitals of appropriate symmetry on ligands. Compounds with metal-metal δ bonds occur in the middle of the transition series. δ bonds are generally quite weak compared to σ and π bonds. For this reason, compounds containing C=C double bonds are very common, but those with Si=Si bonds are rare. π-bonded compounds of heavier elements are rare because the larger cores of the atoms prevent good π-overlap. Because pπ-pπ bonding involves sideways overlap of p-orbitals, it is most commonly observed with second-row elements (C, N, O). In each case, we can make bonding or antibonding combinations, depending on the signs of the AO wavefunctions. Some possible σ (top row), π (bottom row), and δ bonding combinations (right) of s, p, and d orbitals are sketched below. \): The octachlorodirhenate(III) anion, 2−, which has a quadruple Re-Re bond. ![]()
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