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Inorganic Chem > Topic 2 > Flashcards

Topic 2 Flashcards

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1
Q

evolution steps of molecular theory

A

Lewis dot, VSEPR, point groups, character table

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2
Q

Uses of character table

A

info about IR, Uv-vis spectroscopy, NMR, DFT calculation

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3
Q

h=

A

group order. total number of operations (can have more than one in each class)

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4
Q

last 2 columns of character table

A

linear functions and rotations, then quadratic functions

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5
Q

number of irreps =

A

number of classes on table

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6
Q

characters are represented by symbol..

A

chi

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7
Q

character value meanings

A

1 = symmetric, -1 = antisymmetric, 0 = different position

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8
Q

mulliken symbols

A

represent irreps

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9
Q

A, B, E, and T

A

represent dimensions (A and B=1d, E = 2d, T =3d)

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10
Q

A vs B symbols

A

A has Cn (or sigma v if no Cn) symmetry (1), B does not (-1)

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11
Q

1 vs 2 subscripts

A

symmetry at sigma v. 1 = has symmetry (1), 2 does not (-1)

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12
Q

g vs u subscripts

A

g is symmetric at inversion center, u is not

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13
Q

’ or “ for Mulliken symbols

A

’ is symmetric at sigma h, “ is not

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14
Q

A1/Ag/A1g is..

A

always all characters of 1

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15
Q

how to get each row to = group order?

A

sum for each row of squares of characters * number of operations in their class =group order. also just sum of squares of numbers in E irrep

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16
Q

proving irreps are orthogonal

A

summation of C1C2(number of operations) for each character on both rows will = 0

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17
Q

p orbital vs d orbital symmetry

A

p are always u, d are always g (invertible)

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18
Q

what groups have T

A

high symmetry (polyhedrons)

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19
Q

the great orthogonality

A

number of an irrep = 1/h(sum(operations in class)(character of representation)(character from table)) for the whole row

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20
Q

chirality and symmetry

A

can only be Cn, Dn, or T (no I, no Sn, no sigma

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21
Q

polarity and symmetry

A

less symmetrical, usually Cn, Cnv, Cs

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22
Q

harmonic oscillation

A

restoration linearly corresponds to displacement of bonds

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23
Q

force of restoration of bond length =

A

-kx

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24
Q

energy of vibration changes based on..

A

inverse mass, so heavy atoms have less vibration, and bond strength, so strong bonds have more vibration (higher k too)

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25
diatomic modes of vibration
just 1 = stretch/compression
26
non-linear modes of vibration
3N - 6 (the six are from translation and rotation possibilities)
27
symmetric stretching symbol
mu s
28
asymmetric stretching symbol
mu as
29
bending symbol
delta
30
linear molecule modes of vibration
3N - 5 (3 modes translation, 2 rotations)
31
steps to determine vibrational modes
find point groups, assign xyz vectors for the atoms moving, find reducible reps, use those to find irreps, exclude translational and rotational modes, and see which are IR/Raman active
32
IR active means..
dipole moment is changed (symmetry changes). indicated by x, y, z
33
Raman active means
polarization changes (e- move) so changes in atom distance like stretching. indicated by xy, xz, yz, x^2-y^2
34
checking activity based on type of vibration
draw motion arrows on the atom and check that they match symmetry of the irrep they belong to
35
single crystal x ray diffraction
tells shape of molecule, takes days to get back from lab..
36
molecular orbital interference
waves = phase of orbitals (+ or -), can be constructive if synced and destructive if not synced
37
different orientations of 2 orbitals (wrt z axis) means
they cannot form a bond
38
bonding types
constructive = bonding orbital, destructive = anti bonding orbital (gap in e- density btwn the two sides)
39
energy of respective atomic orbitals
if they are close in energy, the bond is stronger
40
simple molecular orbital theory
says that delta E for bonding and anti bonding orbitals is = (opposite)
41
linear combination of atomic orbitals
for 2 orbitals, wave function b (bonding) = a1 + b2, wave function * (antibonding) = c1+ d2, if delta e b = delta e *, coefficients a=d and c=b
42
integrating LCAO
LCAO^2 integrated for all of space = 1, can do same for a1+b2 etc.
43
s
overlap btwn orbitals (>0 for b, <0 for *, 0 for no bond)
44
sigma bonds
no nodal plane containing the z axis (no planes when you rotate around z axis)
45
pi bonds
1 nodal plane containing z axis (ie d orbitals)
46
delta bonds
2 nodal planes on z axis
47
s orbital orientations
can only be head-to-head
48
p orbital orientations
can be head-to-head or face-to-face
49
d orbital orientations
can be head-to-head, face-to-face, side-to-side
50
planning molecular orbitals
draw out valence e- on both sides, and energy levels of each possible orbital in between. fill in orbitals based on energy. energy of orbitals must be checked based on sp mixing
51
bond order=
1/2(e- in bonding - e- in non-bonding)
52
sp mixing
sigma bonds can mix if close in energy and same symmetry, this sends the low energy lower and the higher energy higher
53
which atoms have sp mixing
N2 and lighter
54
why do only light elements have sp mixing
energy diff becomes too big as nuclear charge inc bc s is more stabilized by nucleus and becomes way lower energy than p (10-14 eV)
55
bond order and strength
USUALLY CORRELATE, some double bonds are really weak though
56
frontier orbitals
outer orbitals, determine properties based on where e- will be removed/shared
57
determining which atom in a molecule has activity
closest in energy to orbital with outer e-
58
HOMO
highest occupied molecular orbital (for losing e-)
59
LUMO
lowest unoccupied molecular orbital(for taking on e-)
60
if an atom has the homo and lumo
it can bond AND back-bond = super strong
61
nine steps for polyatomic MOs
3D structure and point group; break down into center and ligands; basis set for center atom orbitals (list the orbitals) and their mulliken symbols from the table; THEN reducible reps for group orbitals/ligand basis set treating all the orbitals together as a single object; irreps for ligand basis set; SALCs - template method; THEN set up the orbitals on energy diagram; mix MOs based on symmetry and energy; fill in electrons.
62
SALCs
symmetry adapted linear combinations
63
template method
match symmetry to inner atom for each orbital based on orientation (where the charge should go/what phase based on proximity basically)
64
dont forget when finding irreps
always check E !!
65
rotational modes
Rx, Ry, Rz. remove these
66
translational modes
x, y, z. remove these one for each, the rest are IR active.

Inorganic Chem (4 decks)

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