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45 Cards in this Set
- Front
- Back
Constructive Interference
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Two waves in same phase
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Destructive Interference
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Two waves in different phase
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Dual Nature of light
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Light undergous both interference and diffraction: wavelenth
Photoelectric effect behaves like a massless paprticle: photon |
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Lambda
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Wavelength= h/(mass x velocity)
where h is Plancks constant |
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De Broglie
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Proved photon nature of light
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Davisson and Germer
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Beam of e- showed deffraction by Al foil: wavelike property
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Line (band) spectrum
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Plot amout of light absorbed or emitted by substance versus wavelength of light
Corresponds to photons of certain energies of light |
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Neils Bohr
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Postulated E levels of e were quantized
when an atom gives off an electron it moves into a higher level |
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Orbital
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The prob of finding an e- around the nucleus ina region of space
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1s
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N=1 l=o
symmetrically positive or negative with high prob at nucleus and exponentially lower with distance |
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2s
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N=2 and l=0
Middle looks like 1s with a node and then a raise and fall in density |
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2p
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N=2 and l=1
Nodal plain in nucleus, density raises and then falls back down |
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Linear Combination of Atomic Orbitals
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Normal covalent bonds half filled orbitals overlap sharing e- and forming bonding molecular orbitals and antibonding orbitals
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Sigma bond
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symmetrical about its axis
Overlapping two s forms sigma and sigma* orbitals End to end overlap of 2 p orbitals forms pi and pi* |
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Valence Shell Electron Pair Repulsion Theory (VSEPR theory)
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In covalent molecules both bonded and lone pairs of e- repel eachother
Molecules assume shape to keep all e- as far away frome each other as possible Solid straight line is on plane Solid Wedge towards reader dash wedge away from reader |
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Linear
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180°
Two atoms bound to central atom, no lone pair |
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Bent
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105°
Two atoms bound to central atom with lone pair |
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Triangular planar
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120°
Three atoms bound to central atom with no lone pair |
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Pyramidal
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107.5°
three atoms bound to central atom w/lone pair |
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Tetrahedral
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109.5°
Four atoms bount to central atom w/no lone pair |
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Bipyramidal
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Five atoms bound to central atom w/no lone pair
Three atoms on (XY) plane, centtral one is on (XZ) plane with other two |
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Octahedral
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Six atoms bound to central atom with no lone pair
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Hybridization
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Mixing of wave equations to form new orbitals with different directions in space from the original atomic orbitals
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sp^3 hybrid
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4 new orbitals from 2s with three 2p
points to corners of regular tetrahedron w/bond angles 109.5° lower E than original |
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sp^2 hybrid
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3 new orbitals from 2s and 2 2p orbitals
Planar 120° w/perpindicular P orbital lower E than original |
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sp hybrid
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2 new orbitals from 2s and 1 2p
lower E than original |
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Polar bonds
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Bond has significant dipole
unequal sharing of e- |
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δ+/δ-
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Partial plus (< full +1 ion charge) or partial minus (< full -1 electron charge) dipole charge
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Some dipole moments (many)
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C-N .22 D (All in D)
C-H .3 C-0 .86 H-I 1.29 H-B 1.48 H-4 1.51 H-CL 1.56 C=0 2.4 C=-N 3.6 |
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Dipole moment
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Net vector sum of individual dipole moment
= partial charge (coulambs) x dostance between atoms (m) |
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Debye
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Conversion factor for dipole moment
3.34 x 10^-30 coulomb meters |
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u in debye units
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4.8 x [delta electron charge] x [distance in angstroms]
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net dipole moment = 0
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No molecular polarity
FF CO2 BF3 CCl4 |
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Stereoisomer polarity
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One may be polar while other is non-polar
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Repulsive intramol forces
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electrons repel each other or nuclei repel each other when too close
Steric hindrance occurse when molecules come to close to each other and are in each others way |
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Attractive intromol forces
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positive nucleus attracts electrosn
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Dipole-Dipole
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Attraction of permanent dipoles
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Hydrogen Bonding
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Special case of strong dipole-dipole bonding with H attached to N, O or F
Carbonyl H not usually H bond Strength ~5-6 kcal/mol |
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London Forces
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Very weak intermol forces netween molecules due to temporary dipoles
In non-p;olar bonds e- temp move closer to one atom creating a dipole inducers short lived dipole formation in a neighboring molecule Increases with surface area |
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Strong Intermolecular forces vs bp and mp
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bp and mp raised by stronger forces
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Solubility of Polar and ionic substances
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dissolve in very polar solvent (ie water, ethyl alc)
Anions H-bond to water and alcohols Cations attracted to lone pairs or partial negatives |
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ΔG = ΔH - TΔS
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s is entropy (disorder), h is enthalpy
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Salt in water
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ΔH is small positive b//c energy is required to seperate Na from Cl but some E is given off by formation of H bonds to cl and the ion-dipole attraction of Na+ for the O of water
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Ionic substance in non-polar solvent
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Does not dissolve, attraction of Na to Cl strong and weak london forces of non-polar solvent not enough to break bonds
ΔH is large positive |
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Small alcohols in water
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misciple with water due to H bonding and increase in S
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