After today you will be able to Explain

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 5: Bonding Molecular Geometry

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 H H ~180˚ 3 atoms O C O – Example: CO 2 Central atom must have NO unshared pairs

Shape: Bent 3 atoms – Example: H 2 O H ~104. 5˚ Central atom can have one or two unshared pairs of electrons

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

Shape: Pyramid 4 atoms – Example: NH 3 H ~107. 5˚ N H H Central atom has one unshared pair

Shape: Tetrahedral 5 atoms – Example: CH 4 H ~109. 5˚ H Central atom has NO unshared pairs H

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

Summary of Shapes Linear Bent Trigional planar Pyramid Tetrahedral Trigional bipyramidal