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45 Cards in this Set

  • Front
  • Back
Constructive Interference
Two waves in same phase
Destructive Interference
Two waves in different phase
Dual Nature of light
Light undergous both interference and diffraction: wavelenth

Photoelectric effect behaves like a massless paprticle: photon
Wavelength= h/(mass x velocity)
where h is Plancks constant
De Broglie
Proved photon nature of light
Davisson and Germer
Beam of e- showed deffraction by Al foil: wavelike property
Line (band) spectrum
Plot amout of light absorbed or emitted by substance versus wavelength of light

Corresponds to photons of certain energies of light
Neils Bohr
Postulated E levels of e were quantized

when an atom gives off an electron it moves into a higher level
The prob of finding an e- around the nucleus ina region of space
N=1 l=o

symmetrically positive or negative with high prob at nucleus and exponentially lower with distance
N=2 and l=0

Middle looks like 1s with a node and then a raise and fall in density
N=2 and l=1

Nodal plain in nucleus, density raises and then falls back down
Linear Combination of Atomic Orbitals
Normal covalent bonds half filled orbitals overlap sharing e- and forming bonding molecular orbitals and antibonding orbitals
Sigma bond
symmetrical about its axis

Overlapping two s forms sigma and sigma* orbitals

End to end overlap of 2 p orbitals forms pi and pi*
Valence Shell Electron Pair Repulsion Theory (VSEPR theory)
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

Two atoms bound to central atom, no lone pair

Two atoms bound to central atom with lone pair
Triangular planar

Three atoms bound to central atom with no lone pair

three atoms bound to central atom w/lone pair

Four atoms bount to central atom w/no lone pair
Five atoms bound to central atom w/no lone pair

Three atoms on (XY) plane, centtral one is on (XZ) plane with other two
Six atoms bound to central atom with no lone pair
Mixing of wave equations to form new orbitals with different directions in space from the original atomic orbitals
sp^3 hybrid
4 new orbitals from 2s with three 2p

points to corners of regular tetrahedron w/bond angles 109.5°

lower E than original
sp^2 hybrid
3 new orbitals from 2s and 2 2p orbitals
Planar 120° w/perpindicular P orbital

lower E than original
sp hybrid
2 new orbitals from 2s and 1 2p

lower E than original
Polar bonds
Bond has significant dipole
unequal sharing of e-
Partial plus (< full +1 ion charge) or partial minus (< full -1 electron charge) dipole charge
Some dipole moments (many)
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
Dipole moment
Net vector sum of individual dipole moment

= partial charge (coulambs) x dostance between atoms (m)
Conversion factor for dipole moment
3.34 x 10^-30 coulomb meters
u in debye units
4.8 x [delta electron charge] x [distance in angstroms]
net dipole moment = 0
No molecular polarity

Stereoisomer polarity
One may be polar while other is non-polar
Repulsive intramol forces
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
Attractive intromol forces
positive nucleus attracts electrosn
Attraction of permanent dipoles
Hydrogen Bonding
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
London Forces
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

Increases with surface area
Strong Intermolecular forces vs bp and mp
bp and mp raised by stronger forces
Solubility of Polar and ionic substances
dissolve in very polar solvent (ie water, ethyl alc)

Anions H-bond to water and alcohols
Cations attracted to lone pairs or partial negatives
s is entropy (disorder), h is enthalpy
Salt in water
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
Ionic substance in non-polar solvent
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
Small alcohols in water
misciple with water due to H bonding and increase in S