Unit 2 Atoms and Bonding 2.91 Molecular Shapes and VSEPRs Textbook ch 9.1 – 9.2 Big Idea 2: Chemical and physical properties of materials can be explained by the structure and the arrangement of atoms, ions, or molecules and the forces between them. Students will be able to demonstrate understanding by laboratory investigation, analysis of data and creation of models. Learning Objectives SWBAT: : • Predict the 3D shapes of molecules using VSPER model Molecular Geometry Hemoglobin SHAPES • This is the 3-D shape of a molecule • Electrons repel each other – Because of this, they adjust their shape to be as far apart as possible • Electrons will repel away from each other to lower the repulsion in the molecule VSEPR Model (Valence Shell Electron Pair Repulsion) The structure around a given atom is determined principally by minimizing electron pair repulsions. Predicting a VSEPR Structure Draw Lewis structure. Put pairs as far apart as possible. Determine positions of atoms from the way electron pairs are shared Determine the name of molecular structure from positions of the atoms. Take out worksheet Skeleton AX Shape Linear Examples # atoms bonded to central atom: # Unbonded pairs of : electrons H2 Picture Skeleton AX2 Shape Linear Examples # atoms bonded to central atom: # Unbonded pairs of : electrons CO2 Picture Skeleton Shape AX3 Trigonal planar Examples # atoms bonded to central atom: # Unbonded pairs of : electrons BF3 Picture Skeleton Shape AX2E bent Examples # atoms bonded to central atom: # Unbonded pairs of : electrons SO2 Picture Skeleton AX4 Shape tetrahedral Examples # atoms bonded to central atom: # Unbonded pairs of : electrons CH4 Picture Skeleton AX3E Shape Trigonal pyramidal Examples # atoms bonded to central atom: # Unbonded pairs of : electrons NH3 Picture Skeleton Shape AX2E2 bent Examples # atoms bonded to central atom: # Unbonded pairs of : electrons H2O Picture Skeleton Shape AXE3 linear Examples # atoms bonded to central atom: # Unbonded pairs of : electrons HCl Picture Skeleton AX5 Shape Trigonal bipyramidal Examples # atoms bonded to central atom: # Unbonded pairs of : electrons PCl5 Picture Skeleton Shape AX4E Seesaw Examples # atoms bonded to central atom: # Unbonded pairs of : electrons SF4 Picture Skeleton Shape AX3E2 T shape Examples # atoms bonded to central atom: # Unbonded pairs of : electrons ClF3 Picture Skeleton Shape AX2E3 linear Examples # atoms bonded to central atom: # Unbonded pairs of : electrons XeF2 Picture Skeleton AX6 Shape octahedral Examples # atoms bonded to central atom: # Unbonded pairs of : electrons SF6 Picture Skeleton Shape AX5E Square pyramidal shape Examples # atoms bonded to central atom: # Unbonded pairs of : electrons BrF5 Picture Skeleton Shape AX4E2 square planar Examples # atoms bonded to central atom: # Unbonded pairs of : electrons XeF4 Picture References http://www.sciencegeek.net/Chemistry/Powerpoints2.shtml I modified his original PPT to fit our needs in AP Chemistry needs. Our textbook: Brown, Lemay et all. AP edition chemistry, 13th edition, 2015