Transition Metals INORGANIC Flashcards
1
Q
What are transition metals?
A
Elements with an incomplete d-subshell that can form at least one stable ion with an incomplete d-subshell
2
Q
What does the Aufbau Principle state?
A
Electrons occupy the lowest energy subshellls first
3
Q
What are the two exceptions from Aufbau principle?
A
Chromium and copper
4
Q
What is the electron configuration for Cr?
A
[Ar]3d⁵4s¹
5
Q
What is the electron configuration for Cu?
A
[Ar]3d¹⁰4s1
6
Q
Why do Cr and Cu have different electron configurations?
A
Energetically more stable
7
Q
What are the four general properties of the transition elements?
A
Variable oxidation states
Form complex ions
Form coloured compounds
Behave as catalysts
8
Q
What are used to represent oxidation state of metal ion?
A
Roman Numerals
9
Q
What is a complex ion?
A
A molecule or ion consisting of a central metal atom or ion with a number of surrounding molecules or ions
10
Q
How do different oxidation states affect formation of complex ions?
A
A different number and variety of ligands can form bonds with transition element
11
Q
Why do transition elements make good catalysts?
A
Due to variable oxidation states
12
Q
How do transition elements behave during catalysis?
A
Can change to various oxidation states by gaining/donating electrons from reagents within reaction
13
Q
What do complex ions consist of?
A
Central metal ion
Ligands
14
Q
What is a ligand?
A
A molecule/ion that forms a coordinate bond with transition metal by donating pair of electrons to bond
15
Q
What charge do ligands have?
A
Negative
Or lone pair to be donated
16
Q
What is the coordination number of a ligand?
A
Number of coordinate bonds to central metal atom/ion
17
Q
What is a monodentate ligand?
A
Ligand that can form only one dative bond to central metal ion
18
Q
What are four common monodentate ligands?
A
Water (H₂O)
Ammonia (NH₃)
Chloride (Cl⁻)
Cyanide (CN⁻)
19
Q
What is a bidentate ligand?
A
Ligand that can form two dative bonds to central metal ion
20
Q
Why can bidentate ligands form two dative bonds?
A
Each ligand contains two atoms with lone pairs of electrons
21
Q
What are two common bidentate ligands?
A
1,2-diaminoethane (H₂NCH₂CH₂NH₂)
Ethanedioate (C₂O₄²⁻)
22
Q
What are multidentate ligands?
A
Ligands containing more than two atoms with lone pairs so can form more than two dative bonds
23
Q
What is an example of a multidentate ligand?
A
EDTA⁴⁻
24
Q
How many dative bonds does EDTA⁴⁻ form with central metal ion?
A
6
25
What kind of ligands are water and ammonia?
Neutral
26
Where is the lone pair in water?
Oxygen atom
27
Where is the lone pair in ammonia?
Nitrogen atom
28
How is overall charge found for complex ions?
Sum of charge on central metal ion and charges on each ligand
29
How many water ligands fit around a central metal ion?
6
30
How many water ligands fit around a central metal ion?
6
31
What kind of ligands are hydroxide and chloride?
Negative
32
How many hydroxide ligands fit around a central metal ion?
6
33
How many chloride ligands fit around a central metal ion?
4
34
What is ligand exchange/substitution?
When one ligand in a complex is replaced by another
35
What is formed by ligand exchange?
A new complex more stable than the original
36
How does ligand exchange affect the charge of a complex ion?
Can change charge or remain same depending on ligands involved
37
How does ligand exchange affect the coordination number of a complex ion?
No changes if ligands similar in size
38
How does ligand exchange affect the geometry of a complex ion?
No changes if ligands similar in size
39
What colour is the cobalt complex [Co(H₂O)₆]²⁺ (aq)?
Pink
40
What colour solution is formed when ammonia is added to [Co(H₂O)₆]²⁺ (aq)?
Pale yellow/straw
41
What is the equation for [Co(H₂O)₆]²⁺ (aq) and ammonia solution?
[Co(H₂O)₆]²⁺ (aq) + 6NH₃ (aq) → [Co(NH₃)₆]²⁺ (aq) + 6H₂O (l)
42
What has happened in following [Co(H₂O)₆]²⁺ (aq) + 6NH₃ (aq) → [Co(NH₃)₆]²⁺ (aq) + 6H₂O (l)?
Complete ligand substituion of water ligands by ammonia ligands
43
What colour solution is formed when excess ammonia is added to [Co(H₂O)₆]²⁺ (aq)?
Brown
44
Why does excess ammonia make [Co(H₂O)₆]²⁺ (aq) brown?
Ligands make cobalt(II) so unstable gets readily oxidised in air to cobalt(III)
45
What is formed when sodium hydroxide is added dropwise to [Co(H₂O)₆]²⁺ (aq)?
Blue precipitate
46
What has happened in following [Co(H₂O)₆]²⁺ (aq) + 2OH- (aq) → Co(OH)₂(H₂O)₄ (s) + 2H₂O (l)?
Partial ligand substitution of two water ligands by two hydroxide ligands
47
What is the equation for [Co(H₂O)₆]²⁺ (aq) and sodium hydroxide?
[Co(H₂O)₆]²⁺ (aq) + 2OH- (aq) → Co(OH)₂(H₂O)₄ (s) + 2H₂O (l)
48
What reasons are there for ligand substitution to be incomplete?
If energetics of reaction and stability of product not favourable
Different sized ligands
49
What is formed when sodium hydroxide is added dropwise to [Cu(H₂O)₆]²⁺ (aq)?
Light blue precipitate
50
What has happened in following [Cu(H₂O)₆]²⁺ (aq) + 2OH- (aq) → Cu(OH)₂(H₂O)₄ (s) + 2H₂O (l)?
Partial ligand substitution of two water ligands by two hydroxide ligands
51
What is the equation for [Cu(H₂O)₆]²⁺ (aq) and sodium hydroxide?
[Cu(H₂O)₆]²⁺ (aq) + 2OH- (aq) → Cu(OH)₂(H₂O)₄ (s) + 2H₂O (l)
52
What is formed when excess conc ammonia is added dropwise to Cu(OH)₂(H₂O)₄ (s)?
Light blue precipitate dissolves to form deep blue solution
53
What is the equation for Cu(OH)₂(H₂O)₄ (s) and excess ammonia?
Cu(OH)₂(H₂O)₄ (s) + 4NH₃ (aq) → [Cu(NH₃)₄(H₂O)₂]²⁺ (aq) + 2H₂O (l) + 2OH- (aq)
54
What happens when concentrated hydrochloric acid is added to [Cu(H₂O)₆]²⁺ (aq)?
Complete substitution of water ligands causes blue solution to turn yellow
55
What is the equation for [Cu(H₂O)₆]²⁺ (aq) and conc hydrochloric acid?
[Cu(H₂O)₆]²⁺ (aq) + 4Cl- (aq) → [CuCl₄]²⁻(aq) + 6H₂O (l)
56
What is haemoglobin?
Natural complex using transition metal ion
57
What does a haem molecule consist of?
Iron(II) as central ion
Oxygen atoms form dative covalent bond
58
What is haem complex used for?
Transporting oyxgen molecules around body in blood
59
Why is it important oxygen molecules aren't good ligands for haem complex?
Bond weakly to iron(II)
Allows them to break off easily to be transported into cells
60
What has oxygen been replaced by in darker red haem complexes?
Carbon monoxide
61
How is carbon monoxide toxic?
Better ligand than oxygen
Binds strongly and irreversibly to iron(II)
Prevents oxygen being carried to cells
62
What is the chelate effect?
Replacement of monodentate ligands with bidentate and multidentate ligands in complex ions
63
What value does ΔGꝋ have in the chelate effect? Why?
Negative
Energetically favourable reaction
64
Why are entropy changes always positive in chelation?
Reactions produce a net increase in number of particles
65
What does the geometry of complex ions depend on?
Size of ligands
Number of dative bonds to central atom
66
What shape complex is formed from central metal atoms with two coordinate bonds?
Linear
180ᵒ bond angles
67
What shape complex is formed from central metal atoms with four coordinate bonds?
Tetrahedral
109.5ᵒ bond angles
68
What alternate shape complex is formed from central metal atoms with four coordinate bonds?
Square planar
90ᵒ bond angles
69
What shape complex is formed from central metal atoms with six coordinate bonds?
Octahedral
90ᵒ bond angles
70
How do complex ions exhibit geometrical isomerism?
Square planar and octahedral complexes with two pairs of different ligands exhibit cis-trans isomerism
71
What counts as exhibition of 'cis' isomer in complexes?
Ligands next to each other
72
What counts as exhibition of 'trans' isomer in complexes?
Ligands opposite to each other
73
How do complex ions exhibit optical isomerism?
Octahedral complexes with bidentate ligands have optical isomers
74
What are optical isomers?
Two forms are non-superimposable mirror images of each other
75
How are transition element complex solutions coloured?
Absorb wavelengths of light in visible light region of electromagnetic spectrum
76
What colour is visible for transition complex solutions?
Complementary colour opposite to that absorbed
77
What is an isolated transition element ion?
One which is not bonded to any ligands
78
What happens when light shines on solution containing transition element complex?
Electron will absorb energy difference between degenerate and non-degenerate orbitals
79
What equation is used to calculate amount of energy absorbed by electrons in transition complex solution?
ΔE = h x v
80
What does h represent in ΔE = h x v?
Plancks constant
81
What does v represent in ΔE = h x v?
Frequency
82
What is electron promotion?
Electron absorbs light energy that excites it from lower energy orbital to higher
83
What happens to frequencies of light not absorbed in transition element solutions?
Combine to make complementary colour
84
What frequency of light is absorbed by transition element complexes?
That which corresponds to exact energy difference between non-degenerate d orbitals
85
What factors affect exact energy difference between non-degenerate d orbitals?
Type of ligand
Coordination number
Oxidation state of metal ion
86
How does type of ligand affect exact energy difference between non-degenerate d orbitals?
Different ligands split d orbital by different energy
87
How does coordination number affect exact energy difference between non-degenerate d orbitals?
Influences strength of metal ion-ligands interactions
Generally involves change in ligands
88
How does oxidation state affect exact energy difference between non-degenerate d orbitals?
Influences strength of attraction between metal ion and electron pairs in covalent bond
89
What is spectroscopy?
Study of interactions between light and matter
90
What is used to find concentration of coloured transition metal ion solutions?
Colorimeter
91
How does a colorimeter work?
Passes different frequencies of light through sample of solution
92
How is a colorimeter used on coloured transition element solutions?
Frequency absorbed is determined by use of coloured filters and detector
Filter is chosen matching part of spectrum where absorption is strongest
Filter is complementary colour
93
How is concentration of coloured transition metal ion solutions found?
Calibration curve made by measuring absorption of standard solutions with known concentrations
Values plotted on graph of absorption against concentration
Unknowns can be found by extrapolating from absorbance down to concentration
94
What is the Beer-Lambert Law?
At lower concentrations the absorbance is directly proportional to the concentration of the coloured species so a straight line graph is obtained
95
What are the limitations of visible light spectroscopy?
Very dark solution can be difficult to get accurate read
Very pale solution may be at limit of colorimeters sensitivity
96
What subshell do transition elements lose electrons from first?
4s
97
Why are electrons lost from 4s first?
Repulsion between electrons in occupied orbitals push 4s into higher energy state
98
Why do transition metals have variable oxidation states?
First few ionisation energies relatively small and close together
Energy difference associated with removing small number of electrons enables easy variety of oxidation state
99
What influences redox potential for transition metal ions?
pH and ligands
100
What transition metal complex ion does Tollen's reagant contain?
Diamminesilver(I)
101
What is the chemical formula for Diamminesilver(I)?
[Ag(NH₃)₂]+
102
What is Tollen's reagent used for?
Distinguishing aldehydes and ketones
103
What happens when aldehyde is tested with Tollen's reagent?
A silver mirror of silver atoms is formed
104
What is a redox titration?
Oxidising agent being titrated against reducing agent?
105
What happens in terms of electrons during redox titration?
Transferred from one species to another
106
What does it mean that redox titrations are self-indicating?
Don't always require indicator
Transition metal ions change colour when changing oxidation state
107
What are two common transition metal ion redox titrations?
Manganate(VII)
Dichromate(VI)
108
What is the reduction equation for manganate(VII) ion?
MnO₄⁻ (aq) + 8H⁺ (aq) + 5e⁻ → Mn²⁺ (aq) + 4H₂O (aq)
109
What colour change is seen in manganate(VII) redox titration?
Purple - colourless
110
What is the reduction equation for dichromate(VI) ion?
Cr2O7- (aq) + 14H+ (aq) + 6e- → 2Cr3+ (aq) + 7H2O (l)
111
What colour change is seen in dichromate(VI) redox titration?
Orange - green
112
What are the two types of catalyst?
Heterogeneous
Homogeneous
113
What is a heterogeneous catalyst?
Catalyst in different physical state from reactants
114
What is a homogeneous catalyst?
Catalyst in same physical state as reactants
115
Why are transition elements often used as catalysts?
Able to form ions with more than one stable oxidation state
Vacant d orbitals
116
What measures can be taken to minimise cost and maximise efficiency of catalysts?
Increasing surface area
Coating inert surface medium with catalyst
117
Where are catalytic converters used for?
Car exhaust boxes to reduce air pollution
118
What is the first step and its equation in the Contact process?
S (s) + O₂ (g) → SO₂ (g)
Roasting sulfur in air to produce sulfur dioxide
119
What is the second step and its equation in the Contact process?
2SO₂ (g) + O₂ (g) ⇌ 2SO₃(g)
Equilibrium reaction catalysed by vanadium(V) oxide
120
What is the third step and its equation in the Contact process?
SO₂ (g) + V₂O₅ (s) → V₂O₄ + SO₃ (g)
Vanadium(V) oxide catalyst converts sulfur dioxide into sulfur trioxide and is reduced to vanadium(IV) oxide
121
What is the last step and its equation in the Contact process?
O₂ (g) + 2V₂O₄ (s) → 2V₂O₅ (s)
Vanadium(V) oxide is then re-generated by reaction with oxygen, fulfilling role as catalyst
122
What does the Contact process show?
A variable oxidation state can be utilised in heterogeneous catalysis
123
What is the Haber process used for?
Industrial production of ammonia
124
What is the main reaction of the Haber process?
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)
125
What catalyst is used in the Haber process?
Iron pellets
126
Why are iron pellets used in Haber process?
Provide large surface area of catalyst
127
How does iron act as catalyst in Haber process?
Surface of iron attracts electrons in hydrogen and nitrogen
Molecules form temporary loose attachments to surface
Known as absorption
128
What is absorption?
Process by which atoms, ions or molecules adhere to surface from gas, liquid or dissolved solid forming film on surface of adsorbent
129
What is meant by poisoning of catalyst?
Tiny quantities of impurities gradually lodge on surface of catalyst binding with active sites and preventing further catalytic reaction
130
How do transition element ions catalyse redox reactions?
Act as both oxidising and reducing agents
131
What is autocatalysis?
Reaction sped up by product which acts as catalyst for reaction
