L5 MTE208 Ionic structures

L5 MTE208 Ionic structures - Ionic Structures MTE208 Fall...

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Ionic Structures MTE208 Fall 2010 Lecture 5 Last revised 10/11/10 5:58 am
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Learning Objectives Determine the fraction of ionic character in a bond Calculate the force between two ions Classify structures by Bravais Lattice Know the definition of a crystal Calculate likely CNs of ions using r/R Predict whether a compound is likely to form a glass, using Zachariasen’s rules Determine stoichiometry, density, APFs, CNs of all ions, given a unit cell Properly index points, lines and planes Draw points, lines and planes, given their indices.
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Types of Bonds Primary Bonds (Strongest bonds) Metallic Covalent Ionic Secondary Bonds (weaker bonds) van der Waals hydrogen bonds
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Ionic Bonds Ionic bonds form between oppositely charged ions Electron transfer is NOT necessary , if you start with ions. The force of attraction is coulombic in nature The ions often have noble gas electron configurations (they are spherically symmetrical)
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When are ionic bonds likely? Large difference in Electronegativity between neighbors Calculate the fraction of ionic character between any two atoms: The larger the fraction, the more ionic. Bonding can be a combination of ionic and other types (mixed ionic-covalent, for example.) Δ = 4 exp 1 character ionic fraction 2 EN
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Calculate Ionic Fraction: NaCl EN(Na) = 0.9 EN(Cl)=3.0 Δ = 4 exp 1 character ionic fraction 2 EN 67%
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Calculate Ionic Fraction: Fe 2 O 3 EN(Fe) = 1.8 EN(O)=3.5 Δ = 4 exp 1 character ionic fraction 2 EN 51%
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Ionic Bonding What will be the strategy for lowering the energy in ionic crystals?
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This note was uploaded on 11/28/2010 for the course MTE 209 taught by Professor Tanyafalten during the Fall '09 term at Cal Poly Pomona.

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L5 MTE208 Ionic structures - Ionic Structures MTE208 Fall...

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