https://www.youtube.com/watch?v=keHS-CASZfc&feature=related

Valence Shell Electron Pair Repulsion Theory (VSEPR Theory): Looking at molecules in 3D!!! Tuesday, December 6th, 2016

Molecular Shape VSEPR theory assumes that the shape of a molecule is determined by the repulsion of electron pairs.

VSEPR Theory Based on Electron Dot (Lewis structures) VSEPR Theory predicts shapes of compounds VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair Repulsion VSEPR predicts shapes based on electron pairs repelling (in bonds or by themselves) Electrons around central nucleus repel each other. So, structures have atoms maximally spread out

VSEPR overview tetrahedral trigonal pyramidal Bent Linear Each shape has a name (you should know these 5) Names of Shapes: tetrahedral trigonal pyramidal Bent Linear trigonal planar

Triangular Planar Bent Tetrahedral Linear Trigonal pyramidal

Example 1: Methane (CH4) Example 2: Ammonia (NH3) Example 3: Water(H2O)

methane, CH4 Tetrahedral 109.5° Bonds are all evenly spaced electrons

.. ammonia NH3 .. .. .. Trigonal Pyramidal Less repulsion between the bonding pairs of electrons

.. .. water, H2O 109.5° (109.5°) 109.5° (107°) 109.5° (104.5°)

.. ..

Bent or V 2 unshared pairs of e’s at top of O repel bonds and force them to bend

Steps to Success Draw the Lewis Structure for each atom - Count up the valence electrons, determine central atom, bond terminal atoms, recount, add lone electron pairs, check & shift to share if necessary Determine VSEPR Structure -- # atoms bound -- # unpaired electrons on central atom Redraw as VSEPR Structure

Example 4: Carbon Dioxide (CO2)

Example 4: Carbon Dioxide (CO2)

Molecule Kit Lab Activity With your partner, you will draw the lewis dot structures for several compounds. You will construct the compounds from the kits provided and sketch your models. Identify the molecular geometry (shape) of your compound from the central atom and label the bond angles. Lastly, determine if you compound is polar or nonpolar (horse & cart)