Information • Textbooks • Media • Resources
Journal of Chemical Education Software
edited by
Jon L. Holmes Nancy S. Gettys University of Wisconsin-Madison Madison, WI 53706
Two Programs for PC-Compatibles: Abstract of Volume 10B, No. 2 1. The Basics of Covalent Bonding Jeffrey R. Reimers and George B. Bacskay Department of Chemistry, University of Sydney, Sydney, NSW 2006, Australia Sture Nordholm Department of Physical Chemistry, Göteborg University, S-41296 Göteborg, Sweden Through a study of the hydrogen atom, hydrogen molecule ion, and hydrogen molecule, The Basics of Covalent Bonding explores the basic principles of atomic structure and covalent chemical bonding. The range and diversity of the problems addressed and the extensive set of help-pages make the program a suitable pedagogical aid at both introductory and advanced levels of undergraduate study. The H atom module explores concepts such as quantization, energy levels, electronic spectra, orbitals (which can be displayed in a number of ways), and the relationship between the quantum and semiclassical Bohr–Sommerfeld descriptions of electronic structure. The section on H2+ introduces molecular orbitals and electron delocalization. It explores the effect of electron delocalization on the energy of the molecule and its importance in understanding the mechanism of covalent bonding. This is accomplished by analyzing the energies and wave functions that are calculated in a minimal basis of 1s atomic orbitals. The H2 module is a natural extension of the H2+ module. It introduces concepts such as the Pauli exclusion principle (antisymmetry requirement, electron spin, electron correlation) and the possibility of constructing molecular wave functions directly from atomic orbitals, as in Valence Bond Theory, or from molecular orbitals. The molecular segments of the program also enable the graphical display of the computed potential energy curves, molecular orbitals, and one- and twoelectron electron densities. For additional information see the preceding article, “The Mechanism of Covalent Bonds”, on pages 1494–1502.
Several screens from The Basics of Covalent Bonding are shown. Some colors have been inverted for clarity in print.
2. DNA Sequencing Update John F. Beck and David L. Bunbury Department of Chemistry, St. Francis Xavier University, Antigonish, NS B2G 1C0, Canada This update to DNA Sequencing (1) offers students the opportunity to become familiar with two of the main procedures for sequencing nucleic acid fragments. The Sanger and Maxam–Gilbert procedures are presented in complementary formats that can be used for self-instruction, as a course assignment, as a virtual lab (or pre-lab) exercise, or as a testing vehicle. Like its predecessor, the updated version is designed for a university-level chemistry, biochemistry, or molecular biology course, but advanced, senior high school students will also find it instructive. The central feature of the package is the generation of a random DNA fragment that is then processed by either the
Sanger or Maxam–Gilbert procedure. The final, color-marked electrophoretic gel (Sanger) or autoradiogram (Maxam–Gilbert) is simulated and presented to the student for interpretation. Students require a prior general knowledge of the DNA base structures and the principles of electrophoresis. Knowledge of the chemistry of the different cleavage procedures is helpful but not necessary to use the package. DNA Sequencing includes an installation program; the two instructional sections, that include test or assignment segments; a package menu; and programs which evaluate and present, for the course instructor, the results of the test/ assignment segments.
Vol. 74 No. 12 December 1997 • Journal of Chemical Education
1503
Information • Textbooks • Media • Resources
The installation program provides an implementation sequence to be followed before the package can be run. It also requests information to customize the package for the particular learning location. Each instructional section is intended to familiarize students with the strategies and methods of the Sanger or Maxam–Gilbert procedure and to provide guided practice at interpreting the resulting physical evidence. Students can use these sections as often as desired. When a student is confident that he or she has learned the particular interpretation technique, the test/assignment segment provides simulations of appropriately visualized electrophoretic gels (as presented in the instructional segments) that can be used as an assignment or test to show mastery of the procedure. The entire instructional package is menu driven with instructions to end the program, get help, and return to the menu constantly on the screen. For the course instructor, programs are provided to evaluate the answers to the test/ assignment segment and present the results on-screen and in an ASCII text file. Literature Cited
Screens from the Maxam–Gilbert procedure (right) and the Sanger procedure (left) are shown.
1. Beck, J. F.; Bunbury, D. L. DNA Sequencing, J. Chem. Educ. Software, 1997, 10 B, No. 1.
Using These JCE Software Programs in the Classroom This issue, Volume 10 B, Number 2 marks the end of Series B, for PC-compatible computers running DOS. Because of declining submissions and the preference of users for Windows, any future DOS submissions will be required to run under Windows and Windows 95. If accepted for publication, they will be published in JCE Software’s Series D, for Windows-compatible computers. We will continue to publish Series C, for Mac OS-compatible computers, and Special Issues on CD-ROM and videotape. How To Use These Programs The Basics of Covalent Bonding is ideal for use as a lecture aid when presenting quantum numbers and atomic orbitals in introductory chemistry. It comes with several lessons designed for more advanced students (physical chemistry, quantum chemistry) to use the program directly. DNA Sequencing can be used as an introduction, assignment, or assessment tool. It may be particularly effective as a pre-laboratory exercise.
Hardware/Software Requirements Hardware and software requirements for this issue are shown below. Ordering and Information Journal of Chemical Education Software (often called JCE Software) is a publication of the Journal of Chemical Education. There is an Order Form inserted in this issue that provides prices and other ordering information. If this card is not available or if you need additional information, contact JCE Software, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1396; phone; 608/2625153 or 1-800-991-5534; fax: 608/265-8094; email:
[email protected]. Information about all our publications (including abstracts, descriptions, updates, etc.) is available from our World Wide Web site: http://jchemed.chem.wisc.edu/
Hardware and Software Requirements Computer
CPU
The Basics of Covalent Bonding
MS-DOS compatible
80486 or higher with math coprocessor
DNA Sequencing
MS-DOS compatible
80286 or higher
Series B
MS-DOS compatible
80286 or higher
1504
RAM
Drives
Free Disk Space
Graphics
System
Other
640 KB
Hard disk, 3.5-in. highdensity floppy drive
1 MB
VGA or better
MS-DOS or IBM PC-DOS 5.0 or higher
mouse
640 KB
Hard disk, 3.5-in. highdensity floppy drive
0.5 MB
VGA or better
MS-DOS or IBM PC-DOS 5.0 or higher
—
640 KB
Hard disk, 3.5-in. highdensity floppy drive
(varies by program)
VGA or better
MS-DOS or IBM PC-DOS 5.0 or higher
—
Journal of Chemical Education • Vol. 74 No. 12 December 1997
