Exam 2 Complete Lectures.pdf - Chem 260 Chemistry 260...

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Chem 260 Lecture 16 1 Chemistry 260 Lecture 16 February 14, 2020 Today in Chemistry 260 • non-covalent interactions (intermolecular forces) • ionic “bonds” • electrostatic interactions & distance • intermolecular forces & distance • hydrogen bonds Next in Chemistry 260 • reading Chang 2.1-4. • gases? Exam #1: Monday, Feb. 17, 6-8 PM Check Canvas announcement for room assignments All alternates have been notified Bring – 1 note sheet (8.5 by 11 both sides), pencils, erasers, calculator Interactions in Chemistry 1. Atoms contain positive nuclei and negative electrons +Ze -e r V r ( ) = 1 4 πε 0 q 1 q 2 r = 1 4 πε 0 + Ze ( ) e ( ) r = 1 4 πε 0 Ze 2 r The ± Coulomb ² potential describes interactions between charged particles The MOST IMPORTANT potential energy function in chemistry e = 1.6022 ³ 10 -19 Coulombs e 0 = 8.85418782 ³ 10 -12 m -3 kg -1 s 4 A 2 Charles-Augustin de Coulomb Consider the points labeled above. For which points is the force between the nuclei repulsive? A. A B. B C. C D. D E. C and D Example: hydrogen molecule A B C D Concept Question Translocation of DNA through a membrane in alpha-hemolysin. Non-bonding interactions are electrostatic, a combination of charges charge distributions “distortability” of charge dist. J. Mathé, A. Aksimentiev, D. R. Nelson, K. Schulten, and A. Meller PNAS USA , 102:12377-12382, 2005. Intermolecular Interactions Ionic Interactions: + - r 1/r long range interaction proportional to the product of charges not directional V ( r ) = q A q B 4 πε o r A B Electrostatic Interactions V ( r ) = | q A q B | 4 πε o r If q A and q B are opposite charge V ( r ) = | q A q B | 4 πε o r If q A and q B are same charge