Chapter 9: Molecular Geometry and Bonding Theories What do the molecules look like and why?

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Chapter 9: Molecular Geometry and Bonding Theories What do the molecules look like and why?

Valence Shell Electron Pair Repulsion Theory (VSEPR) VESPR is a model of how molecules arrange themselves and get their shape. It is based on the idea that the groups of electrons (often called electron domains) around the central atom will repel one another to get as far away from each other as possible. Each non-bonding pair, single bond or multiple bond produces an electron domain around the central atom. There are five possibilities for the arrangement of groups of electrons around the central atom. –2, 3, 4, 5, and 6 groups of electrons

Electron Group Geometry These geometries are called electron group geometries (EGGs) and these are the only possibilities for this. Electron Pairs Around Central Atom Electron Geometry 2Linear 3Trigonal planar 4Tetrahedral 5Trigonal bipyramidal 6Octahedral

Basic Shapes

Molecular Geometries Molecular geometries are the shapes of the molecules when we look at the bonding groups of electrons. The non-bonding groups are the lone pairs and do affect the geometry slightly. The electron domains for non-bonding electron pairs and multiple bonds exert greater repulsive forces on adjacent electron domains and therefore tend to compress bond angles. If there are no lone pairs on the central atom, the molecular and electron group geometries are the same.

Bond Angles…… Look back at pictures and models you built and discuss with table.

Hybrid Orbitals Hybrid orbitals are different for each electron geometry. Electron Pairs Around Central Atom Electron Geometry Hybrid Orbitals 2Linearsp 3Trigonal planarsp 2 4Tetrahedralsp 3 5Trigonal bipyramidal sp 3 d 6Octahedralsp 3 d 2

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