Chapter_09-MolecularGeometry

Chapter_09-MolecularGeometry - Chapter 9. Molecular...

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Chapter 9. Molecular geometry Chapter 9. Molecular geometry Molecular geometry The fact we start with : in molecules the electron orbitals have different shapes from the orbitals in a free atoms in ground states.
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry In beginning, for simplicity, we consider only AB n molecules, like… H 2 O water NH 3 ammonia CO 2 carbon dioxide BF 3 boron trifluoride NO 2 nitrogen dioxide CH 4 methane CCl 4 carbon tetrachloride ClF 3 chlorine trifluoride SF 4 sulfur tetrafluoride SF 6 sulfur hexafluoride IF 5 iodine pentafluoride etc … The question we seek the answer for is: How B n atoms are arranged around the A atom ?
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry Knowledge block 1. – basic 3D shapes Rasmol rotation demo shows these shapes from different directions for better impression -gonal “ means 2D regular shape characterized by a number of sides ; -hedral ” means 3D regular shape characterized by a number of planes (faces) ; We place the central, A, atom into the center of polyhedron and B atoms into its vertices.
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry Derivatives from the basic 3D shapes “Derivatives” here means “part of” Group work: which basic shape can these shapes be derivatives of?
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry Knowledge block 2. – hybridized orbitals When it comes to making chemical bonds then different subshell orbitals (s-subshell, p-subshell and d -subshell) can become similar. (same shape, same energy, but different orientation).
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry sp-hybridization 2 hybrid orbitals are formed : one s- and one p- acquire the same shape (and energy): sp-hybridization.
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry sp 2 -hybridization 3 hybrid orbitals are formed : one s- and two p- acquire the same shape (and energy): sp 2 -hybridization
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry sp 3 -hibridization 4 hybrid orbitals are formed : one s- and three p- acquire the same shape (and energy): sp 3 -hybridization
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Chapter 9. Molecular geometry Chapter 9. Molecular geometry Knowledge block 3 – Valence-Shell Electron-Pair Repulsion model (VSEPR) The rule: each: 1. Non-bonding pair. .. 2. Single bond… 3. Multiple bond… … produces an electron domain (AKA charge cloud ) The rule: Electron domains repulse from each other to create the most stable 3D shape
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Chapter 9. Molecular geometry Domain repulsion and bond angles 1) Non-bonding domains repulse from neighbors stronger than bonding domains (because they have bulky shape). 2) Multiple bonds repulse
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This note was uploaded on 01/02/2012 for the course CHEM 114 taught by Professor Sergeiaksyonov during the Fall '11 term at ASU.

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Chapter_09-MolecularGeometry - Chapter 9. Molecular...

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