Lecture 02 Chemistry Some Basics Fall 2009

Lecture 02 Chemistry Some Basics Fall 2009 - Section 0.2...

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Section 0.2 SOME Basics of Chemistry References: Biophysics, R. Cotterill, Wiley, pp 8-22 For more details on Quantum Theory, see Physical Chemistry for the Life Sciences, P. Atkins and J. de Paula, Chapter 9 and 10. (this extra information is for your interest; it will not be required in exams)
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Atoms Heavy nucleus (protons and neutrons) located at the center Electrons move in the surrounding space at a distance of ~ 0.1 nm (0.1 x 10 -9 m) from nucleus Only certain energy states are permitted for electrons (so-called quantum principle ) Electrons have wave and particle character (wave-particle duality)
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Hydrogen atom and its isotopes
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Hydrogen atom, Carbon atom, and Oxygen atom
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Orbitals Schroedinger equation predicts the permitted energies and the spatial distribution of electrons with respect to the nucleus Different quantum states of an electron near an atomic nucleus are characterized by different spherical and non-spherical probability distributions the so-called orbitals The shapes of these probability distributions of electrons determine the shapes of molecules !!!
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Orbitals II Lowest energy ( ground) state for a hydrogen atom is called 1s state Lowest energy excited state is called 2s state Next higher energy states are the 2p states
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Energy of orbitals
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Orbitals : Distribution of most probable locations of electrons around an atomic nucleus nucleus 1s orbital 2s orbital s orbitals p orbitals
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Shape of d orbitals
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Chemical Binding When two atoms approach each other they exert a force on each other This force can be either attractive or repulsive At short range (<0.07-0.27 nm) the interatomic potential is repulsive , at longer range (>0.07-0.27 nm) it is attractive At a certain distance, the forces are exactly balanced. This interatomic distance determines the density of a material 0.7-2.7 Å Equilibrium bond length (pm): H-H: 74 I-I: 267
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Equilibrium bond lengths
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Ionic bonding between Lithium and Fluorine e
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Ionization energy Energy required to remove an electron from an atom
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Electron affinities
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Lecture 02 Chemistry Some Basics Fall 2009 - Section 0.2...

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