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NAME: _______________________________________ DATE: ___________________ PERIOD: _____ Molecular Geometry Lab VSEPR (Valence Shell Electron Pair Repulsion) is a simple model that employs the concept that electrons, being negatively charged, are repulsive. Therefore, regions of electron densities will attempt to position themselves as far away from one another as possible. OBJECTIVE: Identify the molecular geometry (including angles) of the molecules: CH4, H2O, NH3, CO2, HCl, BF3. INSTRUCTIONS: 1.) Draw a 2D image indicating bond angles in the space above the molecule. 2.) Determine bond angles using the “J-mol” software program. (see below) 3.) Write the name of the type of molecular geometry illustrated by each molecule. (see chart on back) 4.) Construct these molecules with the “ball and stick” model kits to help you determine the geometry. 5.) Write the name of each molecule below the molecular formula. Tips for using the Advanced Molecular Model Set: PLEASE BE CAREFUL – DON’T LOSE ANY PIECES – DON’T MIX UP PIECES BETWEEN KITS – BOX UP KITS NEATLY WHEN YOU ARE FINISHED 1. A hole represents a bonding site or an unshared pair of electrons. 2. Single covalent bonds are represented with wooden pegs. It doesn’t matter if you use the short or long pegs; just use all the same size within one molecule. 3. Multiple covalent bonds are represented with springs. Use 2 springs (and two holes on each atom) for a double bond and 3 springs (3 holes on each atom) for a triple bond. 4. Each kits contains a key for which atoms are represented by which color. a. Use gray (5 holes) for Boron – ignore the two extra holes b. When making the I3- ion, use gray (5 holes) for central iodine atom c. Use yellow (6 holes) for Xenon Tips for using J-mol software: TYPE THE FOLLOWING ADDRESS INTO YOUR BROWSER: http://introchem.chem.okstate.edu/DCICLA/jmol/jmol.php 1. Click and drag on the molecule to rotate. 2. Double click on peripheral atom, single click on central atom, and then drag to another terminal atom to find the bond angle 3. Select the molecular dipole box to see if the molecule is polar. Write the word polar or nonpolar in the space provided on your answer sheet. Add an arrow to your Lewis Structure on the polar substances showing the net pull on the central atom. 4. Use your notes and to determine hybridization and IMF (intermolecular force). Type of Atom Hydrogen Carbon Oxygen Chlorine Boron Nitrogen Fluorine Chemical Symbol Color White Black Red Green Gray Blue Purple CH4 H2O HCl NH3 CO2 BF3
