CHAP09N%20for%20Handouts%206

CHAP09N%20for%20Handouts%206 - Molecular Shapes 1 Areas of...

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1 Molecular Shapes Molecular Shapes 1. Areas of high electron density repel each other , 2. The e- domains arrange themselves as far apart as possible on the central atom. 3. The molecule adopts whichever 3D geometry minimized this repulsion . This controls the geometry around the central atom We call this V alence S hell E lectron P air R epulsion ( VSEPR ) theory. Molecular Geometries: The VSEPR Model Molecular Geometries: The VSEPR Model There are 11 shapes that are important to us: linear (3 atoms, AB 2 ); bent (3 atoms, AB 2 ); trigonal planar (4 atoms, AB 3 ); trigonal pyramidal (4 atoms, AB 3 ); T-shaped (4 atoms, AB 3 ); tetrahedral (5 atoms, AB 4 ); square planar (5 atoms, AB 4 ); see-saw (5 atoms, AB 4 ); trigonal bipyramidal (6 atoms, AB 5 ); square pyramidal (6 atoms, AB 5 ); and octahedral (7 atoms, AB 6 ). •When considering the geometry about the central atom, we consider all electrons (lone pairs and bonding pairs). BUT when naming the molecular geometry, we focus only on the relative positions of the atoms. Predicting Molecular Geometries Predicting Molecular Geometries
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