After today, you will be able to… Explain Valence Shell Electron Pair Repulsion Theory (VSEPRT) Use structural formulas to describe the molecular geometry of atoms Identify the correct geometric name for the shape of the molecule Identify bond angles for molecules

Unit 4: Chemical Bonding Molecular Geometry Day 4 - Notes

Molecular Geometry Valence Shell Electron Pair Repulsion Theory (VSEPR):The electron pairs (both shared and unshared) in the outermost energy level try to get as far apart from each other as possible. –This determines the shape of the molecule.

Shape: Linear 2 atoms –Example: H 2 3 atoms –Example: CO 2 Central atom must have NO unshared pairs HH OC O ~180˚

Shape: Bent 3 atoms –Example: H 2 O Central atom can have one or two unshared pairs of electrons O H H ~104.5˚

Shape: Trigional Planar 4 atoms –Example: CH 2 O Central atom has NO unshared pairs C O H H ~120˚

Shape: Pyramid 4 atoms –Example: NH 3 Central atom has one unshared pair N H H H ~107.5˚

Shape: Tetrahedral 5 atoms –Example: CH 4 Central atom has NO unshared pairs C H H H H ~109.5˚

Shape: Trigional Bipyramidal 6 atoms –Example: PF 5 Central atom has NO unshared pairs For elements in period 3 and higher, when bonded to Cl or F, will have an expanded octet. P F F F F F ~90˚ ~120˚

Summary of Shapes Linear Bent Trigional planar Pyramid Tetrahedral Trigional bipyramidal