chem 141 project argus-1

chem 141 project argus-1 - PART A. Polarity of bond Warm-up...

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PART A. Polarity of bond Warm-up Section Using Argus Lab 4.0 built the following diatomic molecule: H 2 Clean up (click ) the molecule and Save (suggested name: h2) Now calculate surfaces for electron density and electrostatic potential: Go to Calculation then Energy , leave everything as defaulted, except for: QM: PM3 Calculate Properties: Check dipole and Mulliken atomic charges Click on Surface Properties and select (check) the Electron Density and Electrostatic Potential boxes, click OK (twice) and run (click ) Analysis An output file is generated named (h2.out). Use a text viewer to open it (click ). Scroll down towards the end of the file to check the dipole moment length. Record the Dipole moment length here: 0 Debyes What does the dipole moment measures? H measures the polarity of a molecule. Why is it zero for the H 2 molecule? Because the molecule is nonpolar. Record the atomic charges too: Atomic Charge H 0. Should they be equal? Why? Yes, the charge on the atoms cancels the charge on the molecule. . Now create and view the surface: Go to Surfaces. Select QuickPlot ESP mapped density . This generates an electrostatic potential map on the total electron density contour of the molecule. You can make the surface mesh (as shown below) or translucent by right clicking on the surface and selecting Modify Surface . Note: Make sure to click on Select ( ) before doing this operation. You should see the something like this (and a color scheme bar to its left):
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The color bar indicates the charge distribution, from white (high positive) to red (high negative). Finally, obtain the H-H bond length. First switch the surface off the screen by right clicking and doing Hide Surface . Then, right click on the bond (make sure the Select icon is on) and choose Bond Info : H-H Bond length: .7081 Å (angstroms) Playroom: Now it is time to play. Build, clean and save the following molecules (use same settings for H
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chem 141 project argus-1 - PART A. Polarity of bond Warm-up...

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