Previous experiments have suggested that different negative ions are formed by electron transfer to different ends of a molecule. To investigate this possibility, a crossed molecular beam apparatus has been constructed to mass-analyze the ions produced in collisions between fast K atoms and oriented molecules. Initial studies are reported on ion formation in collisions of unoriented SF6 and oriented CH3Br. For lab energies ≈ 5−30 eV, Br- is the only ion observed from CH3Br, and its formation is favored by attack at the Br-end of CH3Br. The Br and CH3 ends have the same energetic threshold for forming Br-. SF5 -, SF6 -, and F- ions are observed from SF6 and O2 - from O2. These ions are formed over a range of energies unlike those formed by electron attachment and suggest that the nascent negative ion can be stabilized by the accompanying positive K+.

Comparisons of free-response and multiple-choice answers reveal different aspects of a student's understanding of complex material. In this study, we developed a series of three-stage Web-based questions for use as pre-instruction assessments of student knowledge of general chemistry. In addition to a free-response and a multiple-choice component, a third component reveals the students' self-assessment skills, providing insight into the "chemistry language" students must know. The results strongly suggest the need for teaching approaches that develop students' ability to critically self-assess their own knowledge and understanding.

Molecular-beam electric-resonance spectroscopy is used to interrogate the rotational states present in a molecular beam of oriented symmetric-top molecules produced for scattering experiments. ∆M ) (1 transitions are observed between Stark energy levels in weak electric fields and depend on the rotational quantum numbers J and K. Substantial rotational cooling is apparent in both neat and seeded beams. Each resonance signal has a complicated dependence upon the high voltage applied to the hexapole focusing fields because molecules in the newly transformed states have vastly different focusing properties from the original. These effects can be unified using a "reduced" focusing voltage that allows intensity comparisons between rotational states, giving rotational temperatures of 3-4 K for CF 3 H seeded in He or Ar. Under favorable circumstances, radio frequency "labeling" might allow one to selectively remove one rotational level at a time from an oriented molecular beam and thereby to study the orientation dependence of different rotational states.

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The periodic table and the periodic system are central to chemistry and thus to many introductory chemistry courses. A number of existing activities use various data sets to model the development process for the periodic table. This paper describes an image arrangement computer program developed to mimic a paper-based card sorting periodic table activity. The advantages of the computer format are described, with a key feature being the ability to playback students’ actions. Being able to observe students working with the data as well as viewing their final answer can allow instructors to identify areas of student difficulty and structure classroom discussion of data analysis and periodic trends to address misconceptions and build on students’ work. Comments on the successful implementation in college general chemistry are included.

Storage and inventory issues are not typically a part of chemistry coursework, yet they are something that a high school science teacher will have to handle immediately upon graduation. Using an authentic scenario and a set of mock chemicals, this activity is engaging and flexible and can be used as either an introduction to safety issues or as a wrap-up and extension and is suitable for a wide range of chemistry and teaching experience levels.

Nanotechnology has been recognized as an important driver of the future economy, and so nanoscience is increasingly being incorporated into the undergraduate chemistry curriculum. This experiment includes the chemical synthesis, optical and chemical testing, and microscopic imaging of gold nanoparticles. Since nanoparticles are too small to measure with optical microscopy, this lab introduces students to atomic force microscopy (AFM). AFM is much more affordable than transmission electron microscopy (TEM). With AFM in dynamic mode, nanoparticles deposited onto a flat surface can be counted and measured with almost the same accuracy as TEM. The vast majority of the thousands of students whom we have taught experience success with this experiment. Introductory students (nonscience majors and general chemistry) work in small groups and experience hands-on demonstrations of the AFM instrument. At the advanced level, we have implemented this experiment in a "flipped" lab. For both student populations, we demonstrate an increase in enthusiasm for science and an understanding of nanotechnology.

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