01-24-2011 Lecture

01-24-2011 Lecture - ElectronSpin To fully explain the...

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Electron Spin To fully explain the details of the emission spectra for the elements, a fourth quantum number is needed: Electron Spin Quantum Number ( m s ). It takes all four quantum numbers (n, l, m l , m s ) to identify an electron that can occupy and orbital The electron can exist in one of two possible spin states – either “spin up,” or “spin down” in a magnetic field The Pauli Exclusion Principle: No two electrons in a given atom can have the same four quantum numbers Spin up +1/2 Spin down -1/2 Since only two values of ms are allowed, a given orbital can only hold two electrons, which have opposite spin
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Summary of Allowed Combina7ons of Quantum Numbers
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Mul7‐Electron Atoms 2+ e 1 - e 2 - Nuc Helium H = PE e(1)Nuc + PE e(1)Nuc + PE e(1)e(2) + KE e(1) + KE e(2) Three energy contributions must be considered in the description of the Helium atom: - The kinetic energy of the electrons - The potential energy of attraction of the electrons with the nucleus - The potential energy of repulsion between the electrons The electron pathways cannot be known precisely and the repulsion energies cannot be calculated exactly Electron Correlation Problem
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This note was uploaded on 10/13/2011 for the course CHEM 101 taught by Professor Fitts during the Fall '08 term at UPenn.

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01-24-2011 Lecture - ElectronSpin To fully explain the...

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