Lecture 20 Review - Arrhenius Concept (1890s) Chem 172...

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1 Chem 172 Advanced Inorganic Chemistry Lecture 21/May 19 Midterm review #2 Acid-Base and Coordination Chemistry Arrhenius Concept (1890s) Arrhenius acids form hydrogen ions in aqueous solution; Arrhenius bases form hydroxide ions in aqueous solution. Bronsted-Lowry Concept (1923) Acids: species with a tendency to lose a hydrogen ions; Bases: species with a tendency to gain a hydrogen ions. Solvent-System Concept The solvent system concept appies to any solvent that can dissocaite into a action (acid) and a an anion (base). Acid: Solute that can increase the concentration of cation; Base: Solute that can increase the conctration of anion. Lewis Concept Acid: electron pair acceptor; Base: electron pair donor. Acid-Base Strength (1) Acid dissociation equilibrium constant (aqueous) pK a (HB) = -LogKa =14 – PK b (B - ) (2) Gas phase proton affinity Inductive effect Steric effect Solvation effect Acid-Base Strength Inductive Solvation Steric Acid-Base Strength Leveling Effect
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2 Theory and Hard and Soft Acid and Bases By Pearson, 1963 Hard: non-Ploarizable Soft: polarizable Hard acid prefers to bind to hard bases, and soft acid prefers to bind to soft bases. Quantitative measures: Absolute hardness = half the difference between the ionization energy and the electron affinity. Soft ness is defined as the inverse of hardness. Theory and Hard and Soft Acid and Bases Theory and Hard and Soft Acid and Bases Coordination Compound ± Coordination complexes: a metal atom or ion and a set of ligands. ± Ligand: an atom, ion or molecules that formally donate electrons to the metal. ± Coordination number: the number of ligands that directly bonds to the central atom. ± Coordination covalent bond : the electrons pairs in the bonding orbital come from the ligands alone; ± The formation of a coordination compound from metal ion and ligand is a Lewis acid and base reaction . Coordination Number and Common Geometry Isomers: same atomic composition, different structures. The number of isomers serves as important experimental evidence to determine the coordination chemistry foundation. Isomers
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3 ± Hydrate Isomers/Solvent Isomers: A complex has water as ligand or as added part of a crystal structure. ± Ionization Isomers: Compound with same formula but give different ions in solution ± Coordination Isomers: A complex with multiple metal ions, with the total ration of ligand to metal ion remain the same, but the ligand attached to specific metal ions change. ± Linkage Isomers/Ambidentate Isomers: A complex with the same ligand but the coordination bond forms through different atom of the same ligand. Structure Isomers Stereoisomers Molecules have the same molecular formula and the same connectivity of atoms, but differ only in the three-dimensional arrangement of those atoms in space; ± Diastereomers/Geometrical Isomers: Atoms or groups of atoms can assume different positions around a rigid ring or bond: cis, trans etc. ± Enantiomers/optical isomers:
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This note was uploaded on 06/27/2010 for the course CHEMISTRY Chem 172 taught by Professor Duan,x. during the Spring '10 term at UCLA.

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Lecture 20 Review - Arrhenius Concept (1890s) Chem 172...

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