Physical Chemistry Final – Flashcards
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Quantum Numbers
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n=size, l=shape, m=orientation, s=spin
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atomic units
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length= Bohr Radius, energy= Hartrees, Masses= amu
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spherical polar coordinates
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(r, theta, tau)...................dV= r^2sin(theta)d(theta)d(tau)dr
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Rotational Constant, B
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h/ (8pi^2IC)
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Franck-Condon Principle
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States that an electronic transition is so fast, compared to nuclear motion, that the nuclear configuration does not change during the electronic transition
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Hybrid Orbital
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Orbital formed by LCAO belonging to same atom
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Valence Bond Theory
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assumption that electrons couple in pairs (w/oppposite spins) to form bonds. *difficult to determine energies of electrons **assumes that electrons are localized to specific atoms
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Bond Order
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[(# of electrons in bonding orbital)-(# of electrons in antibonding orbital)] / (2) ** greater the BO, the stronger and shorter the bond
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MO theory
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correctly predicts the relative bond strength& magnetic behaviour of diatomic molecules
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Hund's Rule
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The state of maximum spin multiplicity has the lowest energy **lowest energy=max spin
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Spin multiplicity
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2lSl + 1 ................... =1 (singlet), 2(doublet), 3(triplett), 4(quartet)
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Pauli Exclusion Principle
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No 2 electrons may have the same set of 4 quantum numbers
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Pauli Principle
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The total wavefunctions including the spin, must be antisymmetric w/ rspt to the interchange of any pair of electrons
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Correspondence Principle (BOHR)
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quantum mechanical result approaches the classical result at high quantum #s
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P branch
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in spectroscopy, (absorption) --> a series of lines that correspond to a unit DECREASE in the rotational quantum # J...................(J = -1)
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Q branch
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Corresponds to changes in vibrational quantum number with no change in rotational quantum #............................................(J = 0 )
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R branch
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corresponds to a unit INCREASE in the rotational quantum # J...................(J = +1)
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Born-Oppenheimer approximation
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allows separate treatment of nuclei and electrons. (ma >> me)
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Moment of inertia
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I=mr^2
