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transition metals Flashcards

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1
Q

where are transition metals found

A

d block

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2
Q

what are transition metals

A

d block elements that can form one or more stable ions with incompletely filled d orbitals

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3
Q

what d block elements are not transition metals

A

scandium and zinc

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4
Q

why isn’t scandium a transition metal

A

scandium only forms one ion Sc³⁺ which has a empty d sub shell
it has configuration [Ar]3d¹4s² when it loses three electrons it has configuration of [Ar]

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5
Q

why isnt zinc a transition metal

A

zinc only forms Zn²⁺ which has a full d sub shell
its configuration is [Ar] 3d¹⁰4s² when it loses two electrons it has a full 3d subshell

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6
Q

transition metals have variable … numbers

A

oxidation

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7
Q

transition metals can have variable oxidation numbers because they form multiple …

A

stable ions

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8
Q

what needs to happen to form a compound or a complex containing an ion with a certain oxidation number

A

energy given out when complex is formed has to be bigger than the energy taken to remove outer electrons and form the ion (the ionisation energy)

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9
Q

transition metals form ions from losing electrons from which subshells

A

4s and 3d

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10
Q

why does it take similar amounts of energy to remove an electron from 4s sub shell and the 3d sub shell

A

because the 4s sub shell and the 3d sub shell have similar energy levels

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11
Q

what happens to the energy released when ions form complexes with increasing ionic charge

A

increases

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12
Q

what is a complex ion

A

metal ion surrounded by dative covalently (coordinately) bonded ligands

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13
Q

what is a ligand

A

a atom ion or molecule that donates a pair of electrons to a central metal atom or ion

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14
Q

what must a ligand have

A

at least one lone pair of electrons or it wont have anything to form a dative covalent bond with

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15
Q

ligands with one lone pair are called

A

monodentate
eg. H₂O: :NH₃ :Cl ⁻ :OH⁻

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16
Q

ligands with two lone pairs are called

A

bidentate

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17
Q

example of bidentate ligand

A

1,2-diaminoethane
NH₂CH₂CH₂NH₂

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18
Q

which ligands can form two dative covalent bonds with a metal ion

A

bidentate ligands

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19
Q

ligands with more than two lone pairs are called

A

multidentate

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20
Q

EDTA⁴⁻ has six lone pairs what ligand is it and how many dative covalent bonds can it form

A

hexadentate ligand/multidentate
and can form six dative covalent bonds with metal ion

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21
Q

what does haemoglobin do

A

transport oxygen around the body

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22
Q

what metal complex is haemoglobin

A

iron(II)

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23
Q

what type of ligand is haemoglobin

A

a multidentate ligand called a haem group

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24
Q

what is a haem group made up of

A

a ring containing 4 nitrogen atoms with iron at the centre

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25
Q

the overall charge on a complex ion is its

A

oxidation number

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26
Q

where would you put the charge on a complex ion

A

outside the square brackets

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27
Q

oxidation number of the metal ion =

A

total oxidation number - sum of the charges of the ligand

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28
Q

work out the charge of the metal ion iron in [Fe(CN)6]⁴⁻

A

total oxidation number = -4
CN⁻ ligand charge = -1
iron oxidation number = -4 - (6 x -1 ) = +2

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29
Q

what is the coordination number

A

number of dative covalent (coordinate) bonds formed with central metal ion

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30
Q

what are usual coordinate numbers

A

6 and 4

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31
Q

if a ligand is small what is the usual coordinate number

A

6

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32
Q

if a ligand is larger what is the usual coordinate number

A

4

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33
Q

why are the ligands positioned as far away from each other

A

because bonding electrons in dative covalent bond of a complex repel each other

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34
Q

what is the shape and bond angle in six fold coordination

A

octahedral shape and all bond angles are 90

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35
Q

what is th shape and bond angle in four fold coordination

A

tetrahedral shape bong angles are 109.5

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36
Q

what is the other occasional four fold coordination

A

square planar where bond angles are 90
eg cis-platin

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37
Q

cis/trans isomerism a form of

A

E/Z isomerism

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38
Q

which shape complex ions can show cis/trans isomerism

A

square planar and octahedral

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39
Q

what happens to the groups in cis isomers

A

they are on the same side

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40
Q

what happens tot he groups in trans isomers

A

same groups opposite each other

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41
Q

what metal complex is cis-platin

A

platinum(II)

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42
Q

what ligands are on cis-platin

A

two chloride ions and two ammonia molecules

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43
Q

what shape is cis-platin

A

square planar and so has bond angles of 90

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44
Q

what is cis-platin used for

A

anti cancer drug

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45
Q

why cant trans-platin be given to patients being treated for cancer

A

its toxic

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46
Q

what happens to 3d orbital when ligands bond to the central ion

A

3d orbital splits into two different energy levels

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47
Q

what orbitals do electrons tend to occupy

A

the lower orbitals

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48
Q

what do electrons need to jump up to higher electron orbitals

A

energy equal to the energy gap

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49
Q

where do electrons get the energy to jump up to higher orbitals

A

from visible light

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50
Q

for larger energy gaps does the frequency of light absorbed increase or decrease

A

increase

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51
Q

what affects the size of the energy gap

A

central metal ion
the central metal ions oxidation number
the ligands
coordination number

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52
Q

what happens to the rest of the frequencies of light that are not absorbed

A

they are transmitted or reflected

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53
Q

what do the transmitted or reflected frequencies of light do

A

combine to make the complement of the colour of the absorbed frequencies

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54
Q

from red to purple light what happens to the frequency

A

frequency increases

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55
Q

what is the complimentary of red

A

cyan

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56
Q

what is the complementary of yellow

A

blue

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57
Q

what is the complementary of green

A

magenta

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58
Q

what is the complementary of cyan

A

red

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59
Q

what is the complementary of blue

A

yellow

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60
Q

what is the complementary of magenta

A

green

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61
Q

if there are no 3d electrons what does this mean in terms of energy

A

no energy can be absorbed

62
Q

if no energy can be absorbed what colour will the compound be

A

white or colourless

63
Q

when solid containing transition metal ion is dissolved in water what happens

A

transition metal will form aqueous complex in solution

64
Q

what happens in a aqueous water complex

A

metal ion is surrounded by water ligands

65
Q

what can the colour of the aqueous solutions do

A

help us identify transition metal that is present

66
Q

what colour is Mn+7/MnO₄⁻

A

purple

67
Q

what colour is chromium+6/Cr₂O₇²⁻

A

orange

68
Q

what colour is magnese+6/MnO₄²⁻

A

green

69
Q

what colour is vanadium+5/VO₂⁺

A

yellow

70
Q

what colour is vandium+4/VO²⁺

A

blue

71
Q

what colour is titanium+3/Ti³⁺

A

purple

72
Q

what colour is vanadium+3/V³⁺

A

green

73
Q

what colour is chromium+3/Cr³⁺

A

green

74
Q

what colour is iron+3/Fe³⁺

A

yellow

75
Q

what colour is titanium+2/Ti²⁺

A

violet

76
Q

what colour is vanadium+2/V²⁺

A

violet

77
Q

what is the colour of magnese+2/Mn²⁺

A

pale pink

78
Q

what is the colour of iron+2/Fe²⁺

A

pale green

79
Q

what colour is cobalt+2/Co²⁺

A

pink

80
Q

what colour is nickel+2/Ni²⁺

A

green

81
Q

what colour is copper+2/Cu²⁺

A

pale blue

82
Q

how many oxidation numbers can vanadium exist in in solution

A

four

83
Q

each reduction reaction has its own

A

reducing potential

84
Q

reduction potentials are another name for

A

electrode potentials

85
Q

reduction potentials allow you to work out if

A

redox reactions involving transition metals are likely to happen

86
Q

what ion does chromium form with oxygen

A

chromate(VI) ions [CrO₄²⁻]
dichromate(VI) ions [Cr₂O₇²⁻]

87
Q

why are chromate(VI) ions [CrO₄²⁻], dichromate(VI) ions [Cr₂O₇²⁻] good oxidising agents

A

because they are easily reduced to Cr³⁺

88
Q

what colour are Cr³⁺ ions when surrounded by 6 water ligands

A

violet

89
Q

why will Cr³⁺ ions in solution sometimes look green

A

because the water ligands can be substituted with impurities eg Cl⁻

90
Q

write the reaction of of dichromate (VI) ions/Cr₂O₇²⁻ with zinc and dilute acid

A

Cr₂O₇²⁻(aq) + 14H⁺(aq) + 3Zn(s) ⟶ 3Zn²⁺(aq) + 2Cr³⁺(aq) + 7H₂O(l)

91
Q

write the second reaction of zinc reducing Cr³⁺

A

2Cr³⁺(aq) + Zn(s) ⟶ Zn²⁺(aq) + 2Cr²⁺(aq)

92
Q

why do you need to use inert atmosphere when reacting zinc with Cr³⁺

A

Cr²⁺ is so unstable that it oxidises straight back to Cr³⁺ in air

93
Q

reaction of Cr³⁺ with hydrogen per oxide in alkaline solution

A

2Cr³⁺(aq) + 10OH⁻(aq) + 3H₂O₂(aq) ⟶ 2CrO₄²⁻(aq) + 8H₂O(l)

94
Q

reaction of 2CrO₄²⁻ with acid

A

2CrO₄²⁻(aq) + 2H⁺(aq) ⇌ Cr₂O₇²⁻(aq) + H₂O(l)

95
Q

what happens when you mix aqueous solution of chromium(II) ions with aqueous sodium hydroxide or aqueous ammonia

A

you get chromium hydroxide precipitate

96
Q

[Cr(H2O)6]³⁺(aq) + 3OH⁻(aq)⟶

A

Cr(OH)3(H₂O)₃ + 3H₂O(l)

97
Q

[Cr(H₂O)₆]³⁺(aq) + 3NH₃(aq)⟶

A

Cr(OH)₃(H₂O)₃ + 3NH₄⁺(aq)

98
Q

what colour is chromium hydroxide precipitate/[Cr(OH)₃(H₂O)₃]

A

a grey green precipitate

99
Q

what does amphoteric mean

A

can react as a acid or base

100
Q

chromium hydroxide is amphoteric so

A

it reacts with both acids and bases

101
Q

chromium hydroxide reacts with both acids and bases so its

A

amphoteric

102
Q

[Cr(OH)₃(H₂O)₃] +3H⁺⟶

A

[Cr(H₂O)₆]³⁺

103
Q

[Cr(OH)₃(H₂O)₃] + 3OH⁻⟶

A

[Cr(OH)₆]³⁻ + 3H₂O

104
Q

if you add excess sodium hydroxide to chromium hydroxide precipitate the H₂O ligands

A

depropanate

105
Q

If you add acid to the chromium hydroxide precipitate, the OH⁻ ligands

A

protonate

106
Q

if you add excess NH₃ to chromium hydroxide precipitate

A

a ligand exchange reaction occurs

107
Q

Cr(OH)₃(H₂O)₃ + 6NH₃(aq)⟶

A

[Cr(NH₃)₆]³⁺(aq) + 3OH⁻(aq) + 3H₂O(l)

108
Q

what is the first steps in making chromium (II) ethanoate

A

*orange sodium dichromate is reduced with zinc in acid solution to form green solution
*Cr₂O₇²⁻(aq) + 14H⁺(aq) +3Zn(s)⟶3Zn²⁺(aq) + 2Cr³⁺(aq) +7H₂O(l)
*and then give blue solution of Cr²⁺ ions
*2Cr³⁺(aq) + Zn(s) ⟶ 2Cr²⁺(aq) + Zn²⁺(aq)

109
Q

what is the second step in making chromium (II) ethanoate

A

*sodium ethanoate mixed with solution and red precipitate of chromium (II) ethanoate
*2Cr²⁺(aq) + 4CH₃COO⁻(aq) + 2H₂O(l) ⟶ Cr₂(CH₃COO)₄(H₂O)₂

110
Q

Cr²⁺ are very easily oxidised what should you do to stop them being oxidised

A

*do experiment in inert atmosphere eg nitrogen
*remove air and all oxygen from all the liquids by bubbling nitrogen through them

111
Q

when ligands are swapped and are of the same size what happens to coordination number and the shape of the complex

A

coordination number does not change and neither does the shape

112
Q

if a small uncharged ligand is substituted for large charged ligand what happens to coordination number and change of shape

A

there’s a change of shape and coordination number

113
Q

[Cr(H₂O)₆]³⁺(aq) + 6NH₃(aq) ⇌
and what is the colour change

A

[Cr(NH₃)₆]³⁺(aq) + 6H₂O(l)
*dark green to purple

114
Q

[Cu(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌
and what is the colour change

A

[CuCl₄]²⁻(aq) + 6H₂O(l)
*pale blue to yellow

115
Q

[Co(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌
and what is the colour change

A

[CoCl₄]²⁻(aq) + 6H₂O(l)
pale pink to blue

116
Q

[Cu(H₂O)₆]²⁺(aq) + 4NH₃(aq) ⇌
and what is the colour change

A

[Cu(NH₃)₄(H₂O)₂]²⁺(aq) + 4H₂O(l)
pale blue to deep blue

117
Q

how is carboxyhemoglobin formed

A

oxygen or water molecule in haemoglobin is replaced in ligand exchange reaction with carbon monoxide

118
Q

why does carbon monoxide poisoning happen

A

because carbon monoxide forms strong dative covalent bonds with iron and doesn’t readily exchange with oxygen or water ligands meaning haemoglobin can’t transport oxygen

119
Q

more stable complexes have a positive or negative entropy change

A

positive

120
Q

why do ligand exchange reactions have small enthalpy change reactions

A

dative bonds are broken and formed strength of bonds broken is similar to the strength of the new bonds so enthalpy change is usually small

121
Q

why does entropy increase when mono dentate ligands substituted with bi dentate ligands or multi dentate ligands

A

because when they are substituted the number of particles in solution increases the more particles the greater the entropy reactions with increase in entropy are more likely to happen

122
Q

which reaction is more likely to happen a reaction with a increase in entropy or a reaction with a decrease in entropy

A

the reaction with a increase In entropy

123
Q

when EDTA⁴⁻ replaces mono dentate ligand why does the complex become more stable

A

because the number of particles in solution increases, the more particles the greater the entropy, the greater the entropy the more stable the complex formed

124
Q

what characteristic do transition element hydroxides have

A

brightly coloured precipitates

125
Q

what happens when you mix aqueous solution of transition element ions with aqueous sodium hydroxide and or aqueous ammonia

A

water ligands are deprotonated in acid base reaction and you get a coloured hydroxide precipitate

126
Q

how can you reverse transition element ions with aqueous sodium hydroxide or aqueous ammonia

A

adding an acid to hydroxide percipitate as the hydroxide ligands will protonate and precipitate will dissolve as soluble meta aqua ions

127
Q

[Cu(H₂O)₆]²⁺(aq) + 2OH⁻(aq)⟶
and what is the colour change

A

Cu(OH)₂(H₂O)₄](s) + 2H₂O(l)
pale blue solution to blue precipitate

128
Q

[Cu(H₂O)₆]²⁺(aq) + 2NH₃(aq)⟶
and what is the colour change

A

Cu(NH₃)₂(H₂O)₄ + 2NH₄⁺(l)
pale blue solution to blue precipitate

129
Q

Cu(OH)₂(H₂O)₄ + 4NH₃(aq) ⟶ [Cu(NH₃)₄(H₂O)₂]²⁺(aq) + 2OH⁻(aq) + 4H₂O(l)
is what type of reaction

A

ligand exchange reaction

130
Q

Cu(OH)₂(H₂O)₄ + 4NH₃(aq) ⟶
and what is the colour change

A

[Cu(NH₃)₄(H₂O)₂]²⁺(aq) + 2OH⁻(aq) + 4H₂O(l)
blue precipitate to deep blue solution

131
Q

[Fe(H₂O)₆]²⁺(aq) + 2OH⁻(aq) ⟶
and what is the colour change

A

Fe(OH)₂(H₂O)₄ + 2H₂O(l)
pale green solution to green precipitate

132
Q

[Fe(H₂O)₆]²⁺(aq) + 2NH₃(aq) ⟶
and what is the colour change

A

Fe(OH)₂(H₂O)₄ + 2NH₄⁺(aq)
pale green solution to green precipitate

133
Q

[Fe(H₂O)₆]³⁺(aq) + 3OH-(aq) ⟶
and what is the colour change

A

Fe(OH)₃(H₂O)₃ + 3H₂O(aq)
yellow solution to an orange precipitate

134
Q

[Fe(H₂O)₆]³⁺(aq) + 3NH₃(aq) ⟶
and what is the colour change

A

Fe(OH)₃(H₂O)₃ + 3NH₄⁺(aq)
yellow solution to orange precipitate

135
Q

[Co(H₂O)₆]²⁺(aq) + 2OH⁻(aq) ⟶
and what is the colour change

A

Co(OH)₂(H₂O)₄ + 2H₂O(l)
pale pink solution to a blue precipitate which turns brown on standing

136
Q

[Co(H₂O)₆]²⁺(aq) + 2NH₃(aq) ⟶
and what is the colour change

A

Co(OH)₂(H₂O)₄ + 2NH₄⁺(aq)
pale pink solution to a blue precipitate which turns brown on standing

137
Q

Co(OH)₂(H₂O)₄ + 6NH₃(aq) ⟶ [Co(NH₃)₆]²⁺(aq) + 2OH⁻(aq) + 4H₂O(l)
is a

A

ligand exchange reaction

138
Q

Co(OH)₂(H₂O)₄ + 6NH₃(aq) ⟶
what’s the colour change

A

[Co(NH₃)₆]²⁺(aq) + 2OH⁻(aq) + 4H₂O(l)
the blue precipitate dissolves to form yellow brown solution

139
Q

why do transition metals make good catalyst

A

because they can change oxidation number by gaining or losing electrons within their d orbitals this means they can transfer electrons to speed up reactions

140
Q

V₂O₅ + SO₂ ⟶ V₂O₄ + SO₃
V₂O₄ + ½O₂ ⟶ V₂O₅
what is happening here

A

*vanadium oxidises SO₂ to SO₃ and is reduced itself
*the reduced catalyst is oxidised by oxygen gas back to its original state
*catalyst ready to do process all over again

141
Q

what are homogenous catalyst

A

catalyst in the same state as the the reactants

142
Q

what state is a homogenous catalyst usually

A

an aqueous catalyst for a reaction between two aqueous solutions

143
Q

how do homogenous catalyst work

A

work by combining with the reactants to form intermediate species and then react to form products and reform the catalyst

144
Q

what is true about the energy needed to form the intermediate species which then reacts to form the products and reform the catalyst

A

the energy needed to form the intermediate is lower than that needed to make the product directly from reactants

145
Q

why is the catalyst always able to catalyse the reaction

A

because its always reformed

146
Q

why is the reaction between iodide ions and peroxodisulfate (S₂O₈²⁻) really slow

A

because the ions are both negatively charged so they repel each other so its unlikely they’ll collide and react

147
Q

why doe the reaction between peroxodisulfate (S₂O₈²⁻) ad iodide ions become faster when you add Fe²⁺ ions

A

because each stage involves a positive and negative ions so there’s no repulsion

148
Q

write the reactions between peroxodisulfate (S₂O₈²⁻) ad iodide ions when you add Fe²⁺ ions

A

*S₂O₈²⁻(aq) + 2Fe²⁺(aq) ⟶ 2Fe³⁺(aq) + 2SO₄²⁻(aq)
*2Fe³⁺(aq) + 2I⁻(aq) ⟶I₂(aq) + 2Fe²⁺(aq)

149
Q

*S₂O₈²⁻(aq) + 2Fe²⁺(aq) ⟶ 2Fe³⁺(aq) + 2SO₄²⁻(aq)
*2Fe³⁺(aq) + 2I⁻(aq) ⟶I₂(aq) + 2Fe²⁺(aq)
explain what’s going on

A

*first the Fe²⁺ ions are oxidised to Fe³⁺ ions by S₂O₈²⁻
*the newly formed intermediate Fe³⁺ ions now easily oxidise the I⁻ ions to iodine and the catalyst is regenerated

150
Q

what is autocatalysis

A

Autocatalysis the term used to describe a reaction which is speeded up by a product which acts as a catalyst for the reaction

151
Q

how can you reduce Cr₂O₇²⁻ to Cr³⁺ and Cr²⁺

A

using zinc in acidic conditions

chem (16 decks)

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