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CHEM411 > Module 1+2+3 > Flashcards

Module 1+2+3 Flashcards

1
Q

what does the term ‘lanthanides’ refer to

A

elements from Ce-Lu

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2
Q

what does the term ‘lanthanoids’ refer to

A

elements from La-Lu

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3
Q

what does the term ‘rare earths’ refer to

A

elements from La-Lu, Sc and Y

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4
Q

what does the term ‘actinides’ refer to

A

elements from Th-Lr

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5
Q

what does the term ‘actinoids’ refer to

A

elements from Ac-Lr

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6
Q

what are 2 early applications of the f-elements

A 
gas mantle
pyrophoric alloy (lighter flint)
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7
Q

what compound was found in a gas mantle and what did it do

A

CeO2

coverted light from gas lamp to heat - significantly brighter

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8
Q

what are 3 fields of use for lanthanoids

A

magnetic
optical
materials

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9
Q

what applications do lanthanoids have in magnetics

A

rare earth magnets (Nd) - used in wind turbines

MRI contrast agents

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10
Q

what applications do lanthanoids have in the optical field

A

security inks
lasers
lighting

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11
Q

what applications do lanthanoids have in materials

A

can form specialist alloys

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12
Q

what are 2 key applications of actinoids

A 
nuclear power (235U)
long life batteries (238Pu)
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13
Q

which are the 3 most abundant lanthanoids

A

La, Ce, Nd

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14
Q

which is the only lanthanoid not found in nature and why

A

Pm - radioactive

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15
Q

what 2 common elements are less abundant than lanthanoids

A

iodine

mercury

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16
Q

what are the 2 main mineral structures of lanthanoid sources

A

LnFCO3 - Bastnaesite

LnPO4 - Monazite

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17
Q

what are the top 4 locations with reserves and what percentage do they hold of rare earths

A

china 1/3
vietnam 1/6
brazil 1/6
russia 1/6

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18
Q

where are 97% of rare earths produced

A

china

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19
Q

elements above what atomic number and element are radioactive

A

83 (Bismuth)

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20
Q

how does the abundance of actinoids compare to lanthanoids

A

much lower

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21
Q

which are the 2 actinoids that exist in more than trace amounts

A

U 2.4 ppm

Th 12 ppm

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22
Q

what is the uranium decay series

A

235U - 231Th - 231Pa - 227Ac — 207Pb

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23
Q

what % of U is 235U

A

0.7%

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24
Q

what is the synthetic route of Ac from Ra

A

226Ra - 227Ra - 227Ac

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25
Q

what is the synthetic route of Th - Pa

A

230Th - 231Th - 231 Pa

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26
Q

what is the synthetic route of U - Pu

A

238U - 239U - 239Np - 239Pu

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27
Q

what is the synthetic route of U - Fm

A

238U + 17n - 255U - 255Np - 255Pu — 255Fm

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28
Q

what are some practical difficulties of working with actinoids

A 
radioactive
toxic
v small quantities
many isotopes are unstable
causes unwanted chemical reactions
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29
Q

what are the 2 techniques used to overcome practical problems with working with actinoids

A

tracer techniques

ultra microchemical techniques

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30
Q

what are tracer techniques

A

use v small conc (10-12M) doped into non radioactive substance
monitor radioactivity
trace what happened to An

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31
Q

what are ultra microchemical techniques

A

v small volumes used at normal conc

done under microscope

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32
Q

how many f orbitals per shell

A

7

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33
Q

how many angular nodes does z3 have

A

0

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34
Q

how many angular nodes does yz2 have

A

1

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35
Q

how many angular nodes does z(x2-y2) have

A

2

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36
Q

how many angular nodes does x(x2-3y2) have

A

3

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37
Q

how does the electronic configuration of Ln3+ ions change

A

fills sequentially

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38
Q

what are the anomalies in the electronic configurations of Ln atoms

A

La - fills 5d1 not 4f1
Ce - fills 5d1 4f1 not 4f2
Gd- fills 4f7 5d1 to maintain half filled shell

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39
Q

which Ln can form 4+ and why

A

Ce4+ - stable as 4f0

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40
Q

which 2 Ln elements have stable 2+ ions and why

A

Yb2+ - forms 4f14

Eu2+ - forms 4f7

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41
Q

how does the electronic figuration of An3+ go

A

sequentially as with Ln3+

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42
Q

what is notable about the electronic configuration of early An atoms

A

6d1 is filled instead of 5f up to Pu

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43
Q

what is notable about the electronic configuration of Lr

A

7p is more stable than 6d due to relativistic effects

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44
Q

why do some f elements experience relativistic effects

A

as charge density increase the speed of core electrons increases to stay in orbit - for late f elements this is near the speed of light

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45
Q

what is the formula of mass at high velocity

A

m = m0/root(1-(v/c))

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46
Q

what is the formula for the bohr radius

A

a0 = 4piE0(h2/me2)

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47
Q

what is the relationship between bohr radius and mass

A

as mass increases bohr radius increases

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48
Q

what is the effect of relativistic effects

A

s and p contract - increases shielding

f and d expand - closer in energy

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49
Q

why are early An elements similar to TMs

A

5f and 6d can bond as they are less sheilded

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50
Q

what is the coordination of Ln atoms in the metallic state

A

12 coordinated

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51
Q

what is the general trend of metallic radii across the period

A

radius decreases right to left

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52
Q

what are the 2 exceptions to the generic trend of metallic Ln atoms atomic radius

A

Eu and Yb

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53
Q

why are Eu and Yb larger when in a metal

A

they exist as 2+ ions in electrons whereas the rest exist as 3+
they are 2 plus becasue full and half filled f shells are stable

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54
Q

what is the trend of ionic radii for 3+ Ln ions

A

decreases left to right across period

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55
Q

what is the trend for metallic radii for An

A

decreases Ac-Np (similar to TM)

decreases from higher value Am-Cf

56
Q

what is the trend is ionic radius for 3+/4+ ions

A

gradually decrease across period

3+>4+

57
Q

why are the first and second ionisation energies constant for Ln

A

it refers to the removal of 2 s electrons

58
Q

what are the exceptions for the trend for the 3rd ionisation energies how do they relate to the rest

A

larger for Eu and Yb as they are stabilised as 2+ ions due to filled and half filled f sub shells

59
Q

why is the 4th ionisation energy so high for La

A

the La3+ ion is a xenon configuration

60
Q

why are the 4th ionisation energies for Ce and Tb low

A

they have f0 and f7 configuration for 4+ ions

61
Q

why is the standard energy of reduction almost constant across the Ln series

A

as ionisation potential increases ^hyd increases due to increased ionic radius

62
Q

what is the general trend for hydration enthalpies across the series

A

gradually increase (get more negative) across the series

63
Q

what is the formula for calculating hydration enthalpy

A

^hyd= z^2/r

64
Q

how does the stability of An3+ change across the series

A

increases left to right

65
Q

which An elements can have oxidation states of 2,3,4,5 and 6

A

U, Np, Pu

66
Q

what is the highest ox state for Ac

A

3

67
Q

what is the most stable ox state for Ln elements

A

3

68
Q

at what pH can Ce4+ undergo hydrolysis

A

0

69
Q

what are 2 key features of An4+ ions

A

high charge density

strongly bronsted acidic

70
Q

how is the rate of hydrolysis linked to charge density

A

as charge density increases, rate of hydrolysis decreases

71
Q

what ions can An5+/6+ form

A

actinyl ions ([AnO2]+), [AnO2]2+

72
Q

what elements are the 5 and 6 ox states important for

A

U, Np, Pu, Am

73
Q

what is the evidence for 6p(z)5f(z3) hybridisation

A

short An-O distance

IR absorbtion at 930cm-1 (O-U-O)

74
Q

which orbitals in An can interact with 2p in oxygen and why

A

6d and 5p

they are the correct distance from the U nucleus in the radial distribution diagram

75
Q

is complex formation in aqueous solution endo or exothermic and why

A

endothermic as there is a very large ^hyd

76
Q

how stable are aquo ions for Ln and An

A

they are very labile

77
Q

how do ligands coordinate to an aquo complex

A
  1. form an outsphere complex (attracted to near to complex)

2. form an innersphere complex (replaces H2O around metal)

78
Q

what is the order of increasing stability constants for inorganic ions

A

NO3-

79
Q

what is the order of increasing stability constants for the halides

A

I->Br->Cl->F-

80
Q

what is the formula for ^G of a complex

A

^G=-RTlnbeta

81
Q

what is the formula for beta

A

B=[ML]/M^aLb

82
Q

what is the usual value of ^rH

A

positive

83
Q

what is the usual value for ^rS

A

large and positive

- cancels out large negative ^hyd

84
Q

what type of ligands are normally required to form a stable complex

A

chelating ligands

85
Q

give 3 examples of multidentate ligands

A

P3O10 5-
EDTA 4-
DTPA 5-

86
Q

how does Ln change across the period and why

A

increases as r decreased

87
Q

how does Ln be change as higher dentate ligands are used

A

Increases

88
Q

why does the stabilty of DTPA complexes decrease after Py

A

DTPA isnt very flexible so isnt as stable on smaller elements

89
Q

how do the kinetic of H2O exchange change across the series

A

first half follows Id mechanism

second half follows IA mechanism

90
Q

why does the mechanism of H2O exchange change

A

In early elements they are 9 coord so can loose but not gain

in late elements they are 8 coord so can gain but not lose

91
Q

when is H2O exchange fastestr

A

when energy different between 8 coord and 9 coord complexes is similar (middle of period)

92
Q

what is the trend in the kinetics of forming oxalate complexes

A

faster for early elements

93
Q

explain the trend in kinetics of Ln oxalate formation

A

there is a constant Id mechanism this is faster for the early elements as they are 9 coord so their bonds are longer and easier to break

94
Q

what is the gadolinium break

A

an observation that gadolinium is often in the middle in trends as the 8 coord and 9 coord complexes are of similar energy

95
Q

what do good donors tend to contain

A

acidic oxygens
nitrogen donors
sulfonic acid groups
phenolic groups

96
Q

give an example of a ligand that forms a kinetically inert lanthanide complex and why

A

schiff base (6N in macrocycles) completely surrounds metal

97
Q

what does kinetically inert mean

A

cannot be formed in water as not thermodynamically stable but if formed then added to water there is no easy route to break them down

98
Q

describe the coordination chemisty of the actinyl ion

A

equitorial positions are labile, axial are inert

99
Q

decribe the trend of strength of complex formation for An ions

A

An4+>AnO2 2+> An3+> AnO2+

100
Q

how does Pu(IV) work as a poison

A

similar charge density to Fe(III) so can fill iron stores

  • disrupts iron chemistry
  • releases radiation
101
Q

what are the ligand requirements of a sequestering agent

A

non toxic

stable and soluble at physiological pH

102
Q

what are the 2 geometries for 6 coordinate complexes

A

octahedral

trigonal prism

103
Q

what is the known geometry of a 7 coordinate complex

A

pentagonal bipyramidal

104
Q

what are the 2 known geometries for 8 coordinate complexes

A

cube

square antiprism

105
Q

what is the geometry for a 9 coord complex

A

tricapped prism

106
Q

what is the geometry for a 12 coord complex

A

icosahedron

107
Q

what is a hepaleptic complex

A

complexes with multiple ligand types

108
Q

what are the 2 common classes of neutral oxygen donors

A

polyethers

phosphine oxides/ phosphates

109
Q

how does bonding with a metal ion vary for 15-c-5, tetraglyme and 18-c-6

A

15-c-5 sits under the metal ion as the cavity is not large enough to fit the ion inside
tetraglyme and 18-c-6 fit around the metal ion well

110
Q

how does logB change across series for tetraglyme

A

decreases as the ions get smaller do to steric hinderance of Me groups

111
Q

why does 18-c-6 have a greater stability constant than 15-c-5

A

more donors present

112
Q

why is 18-c-6 more stable for early Ln

A

better fit around metal

113
Q

how do stabilities of cyclic and acyclic compounds compare

A

cyclic ligands are more stable than acyclic

114
Q

how does 18-c-6 complex with the actinyl ion

A

has to distort to fit well

actinyl ions are small

115
Q

describe the lewis acidity of phosphine oxides and phosphates

A

strong lewis bases

116
Q

what are the 3 main types of neutral nitrogen donors

A

aliphatic amines
aromatic N donors
schiff base macrocycles

117
Q

how do stability constants for aromatic amines vary across series

A

increases as M-L bond length decreases

118
Q

how do the stability constants of aliphatic amines change as more N donors are added

A

increase

119
Q

what complex will form in the reaction LnX3 + ligands ->

A

LnLx if X is weakly coordinating

LnX3Lx if X is strongly coordinating

120
Q

why can naphthyridine have a high coordination number

A

has small bite angle

121
Q

what happens in a schiffs base reaction

A

2 x 2,6-diketopyridine is attacked by 2x en to form a cyclic structure which wraps around metal ligand

122
Q

how can An3+ ligands be separated from Ln3+ ligands

A

use BTBP ligand - N is enhanced due to alpha effect

binds more strongly to Am/Cm than to Eu

123
Q

give examples of anion O donors

A

acac (B-diketonates)
alkoxides
phenoxides

124
Q

what 3 properties of B-diketonates can be tuned

A

solubility
volatility
lewis acidity

125
Q

what is the least sterically demanding B-diketonate

A

cannot cover coordination sphere for La3+

fits Yb3+

126
Q

how are B-diketonate complexes formed

A

remove of proton on B-oxygen with bases

reaction with MXn

127
Q

give some properties of B-diketonates

A

Insoluble in water

reasonably volatile

128
Q

what is a use of B-ketonates

A

in MOCVD

metal organic chemical vapour deposition

129
Q

how do the structures of alkoxide complexes changw with ligand size

A

small - trimers
medium - dimers
large - monomers

130
Q

what are the expections to the common rule that Ln3+ is the standard charge

A

Ce4+
Eu2+
Yb2+

131
Q

how do anionic bonds vary to neutral bonds

A

anionic bonds are shorter

132
Q

what are the main type of anionic N ligands

A

silyl amides

133
Q

what are 2 key features of silyl amides

A

very large

stabilise low coordination numbers

134
Q

what are 2 reactions that silyl amide complexes can undergo

A

ligand substitution with phenoxide

adduct formation with phosphine oxides

135
Q

what structure is formed when silyl amides are involved in forming complexs with Ln2+

A

[Ln(N(SiMe2)2L2]

136
Q

what 3 actinides are silyl amides known to complex with

A

U, Np, Pu

CHEM411 (5 decks)

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