Abstract
    The optimized geometry, HOMO, LUMO, electrostatic potential, and partial atomic charges were calculated for chlorine, carbon disulfide, and nitrobenzene at different levels of molecular theory. The different levels of molecular theory were 6-21G, 6-31G, DZV, AM1, and PM3. DZV was the level of theory that was found to be most effective at performing the calculations.

Introduction
    Knowing the electronic structure of a molecule is important because it allows one to understand the reactivity of the molecule. There are many molecular properties that can be predicted about the molecule if the electronic structure is understood. Some of these properties are dipole moments, polarizability, vibrational frequencies, probability of absorption of light and the tendency of the molecule to donate electrons during a reaction. In the past electronic structure calculations had to be done with a pen and paper but thanks to the processing ability of modern computers the calculations can now be done with computer programs.
    In this experiment, the electronic structure of three different molecules was calculated using three different computer programs. The program called Avogadro was used to build the initial structure of the molecules. This program allows the user to build a molecule by drawing in the atoms and bonds of the molecule. Once the molecule has been constructed the program can then calculate the optimized geometry of the molecule. Once a molecule was constructed in Avogadro the file could then be opened in the program MacMolPlt. The MacMolPlt program takes a geometry optimized molecule and builds a file for the molecule that selects the different types of calculations that will be run on the molecule. Some of the different calculations include vibrational frequency calculations, adding diffuse functions to improve dipole moments, potential energy and bond length, and UV-Vis transition energy calculations. Once a file was created in MacMolPlt it could be opened in the GAMESS program. The GAMESS program performs the calculations that were selected in the input file that was created in MacMolPlt. The program runs the input file and creates a .log file that contains the calculated results of the electronic structure calculations.
     The three molecules that were analyzed in this experiment were chlorine, carbon disulfide, and nitrobenzene. The calculations that were performed on all three molecules were geometry optimization, highest occupied molecular orbital, lowest unoccupied molecular orbital, electrostatic potential, partial atomic charges, and dipole moment. In addition to these calculations the vibrational frequency was calculated for chlorine, the dipole moments at each level of theory were calculated for nitrobenzene, and UV-Vis transition energy was calculated for nitrobenzene.

The following links show the calculated values for each molecule:
chlorine
carbon disulfide
nitrobenzene