Chapter 24 - Transition metals Flashcards
(105 cards)
1
Q
Where are the d-block elements located ?
A
- Between group 2 and group 13 on the periodic table
- From scandium to zinc
2
Q
Why are they called the d-block elements ?
A
- The highest energy subshell is 3d
- Highest energy electrons are in the 3d orbitals
3
Q
What are the general properties of d-block elements ?
A
- Metallic
- Strong
- High MP + BP
- Conduct electricity and heat
4
Q
How should you write the electron configuration for d-block elements ?
A
3d and then 4s
5
Q
Which two d-block elements have anomalous electron configurations ?
A
- Chromium
- Copper
6
Q
Why do chromium and copper only have 1 electron in the 4s orbital ?
A
- This is because of stability
- It is believed that a 3d5 and 3d10 subshell gives additional stability to atoms of chromium and copper
7
Q
When forming positive ions from their atoms, what do they lose first ?
A
They lose the 4s electrons first and then the 3d electrons
8
Q
Define transition metals
A
D-block elements that form at leat one ion with a partially filled d orbital
9
Q
What two elements in the d-block are not transition metals ?
A
- Zinc
- Scandium
10
Q
Why are scandium and zinc not d block elements ?
A
Their ions have full d orbitals
11
Q
What are the properties of transition metals ?
A
- Form compounds in which the transition element has different oxidation states
- They form coloured compounds
- The elements and their compounds can act as catalysts
12
Q
What does it mean when it is said that transition metals have variable oxidation states ?
A
They can form compounds with more than one oxidation state
13
Q
What is the pattern of oxidation states like for transition metals ?
A
The number of oxidations states increases until manganese and then decreases
14
Q
What oxidation state do all transition metals have ?
A
They all form compounds with an oxidation number of +2
15
Q
What is the colour of titanium (+3) ?
A
Purple
16
Q
What is the colour of vanadium(+2) ?
A
Purple
17
Q
What is the colour of vanadium (+3) ?
A
Green
18
Q
What is the colour of vanadium (+4) ?
A
Blue
19
Q
What is the colour of vanadium (+5) ?
A
Yellow
20
Q
What is the colour of chromium (+2) ?
A
Blue
21
Q
What is the colour of chromium (3) ?
A
Green
22
Q
What is the colour of chromium (+6) ?
A
Orange
23
Q
What is the colour of manganese (+2) ?
A
Pale pink
24
Q
What is the colour of manganese (+4) ?
A
Dark pink
25
What is the colour of manganese (+6) ?
Green
26
What is the colour of manganese (+7) ?
Purple
27
What is the colour of iron (+2) ?
Light green
28
What is the colour of iron (+3) ?
Yellow
29
What is the colour of copper (+2) ?
Pink
30
What is the colour of copper (+3) ?
Green
31
What colour is Nickel (+2) ?
Green
32
What colour is Copper (+2) ?
Blue
33
What are the 4 reactions in which transition metals act as catalysts ?
- Haber process - Iron catalyst
- Contact process - Vanadium oxide catalyst
- Manufacture of margarine - Nickel catalyst
- Decomposition of H2O2 - Manganese oxide catalyst
34
Give 2 example of homogenous catalysts (transition metal)
- Reaction between iodide ions and peroxodisulfate ions - Iron ions catalyst
- Zinc metal reacting with acids - Copper ions catalyst
35
What is a complex ion ?
A complex ion is formed when one or more molecule/negatively charged ions bond to a central metal ion
36
What is a ligand ?
A ligand is defined as a molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond
37
What is a coordinate bond ?
A covalent bond that is formed when one of the bonded atoms provides both of the electrons for the shared pair
38
What is the coordination number ?
It indicates the number of coordinate bonds attached to the central metal ion
39
It indicates the number of coordinate bonds attached to the central metal ion
A ligand that is able to donate one pair of electrons to a central metal ion
40
What are the neutral monodentate ligands ?
- H2O
- NH3
41
What are the charged monodentate ligands ?
- Halide ions
- CN-
- OH-
42
What are bidentate ligands ?
Ligands that can donate two lone pairs of electrons to the central metal ion
43
What are the two common bidentate ligands ?
- 1,2 - diaminoethane
- ethanedioate ion
44
What are the most common coordination numbers ?
4 and 6
45
What shape does a coordination number of 6 give ?
Octahedral
46
What shapes do a coordination number of 4 give ?
- Tetrahedral
- Square planar
47
When does a square planar shape occur in complex ions ?
Occurs in complex ions of transition metals with 8 electrons in the highest energy d sub shell
48
Which three metals can form a square planar complex ion ?
- Platinum(II)
- Palladium(II)
- Gold(III)
49
What is stereoisomerism ?
Same structural formula but a different arrangement of the atoms in space
50
What types of stereoisomerism can complex ions display ?
- Cis/trans
- Optical
51
For complex ions, what does the type of stereoisomerism depend on ?
- The number and type of ligands that are attached to the central metal ion
- The shape of the complex
52
What complex ions show only cis-trans isomerism ?
Some 4 coordinate and 6 coordinate complex ions that contain two different monodentate ligands
53
What complex ions show optical and cis-trans isomerism ?
Some 6 coordinate complex ions containing monodentate and bidentate ligands
54
Are double bonds needed for cis trans isomerism in complex ions ?
No
55
What dictates the cis trans isomerism in complex ions ?
The central metal atom
56
For square planar, what is the cis isomer ?
- Two identical groups are adjacent to each other
- Coordinate bonds between the identical ligands are 90 degrees apart
57
For square planar, what is the trans isomer ?
- Two identical groups are opposite each other
- Coordinate bonds between the identical ligands are 180 degrees apart
58
For octahedral, what is the cis isomer ?
- Two identical groups are adjacent to each other
- Coordinate bonds between the identical ligands are 90 degrees apart
59
For octahedral, what is the trans isomer ?
- Two identical groups are opposite each other
- Coordinate bonds between the identical ligands are 180 degrees apart
60
For optical isomerism in octahedral complexes, what does their need to be ?
They have to have two or more bidentate ligands
61
What are optical isomers ?
- Enantiomers
- Non superimposable mirror images of each other
62
Can trans isomers form optical isomers ?
No
63
Why cant trans isomers form optical isomers ?
A mirror image is exactly the same and can be superimposed
64
What is a ligand ?
A molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate or dative bond
65
What is a ligand substitution reaction ?
One in which one ligand in a complex ion is replaced by another ligand
66
What is formed when copper (II) sulphate is dissolved in water ?
[Cu(H2O)6]2+ is formed in aqueous solution
67
What colour is the [Cu(H2O)6]2+ ion ?
Pale blue complex ion
68
What happens when excess ammonia is added to a solution containing [Cu(H2O)6]2+ ?
The pale blue solution changes to form a dark blue solution
69
What is the equation for [Cu(H2O)6]2+ reacting with excess ammonia ?
- [Cu(H2O)6]2+ + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 4H2O
- Pale blue solution to a dark blue solution
- However both are octahedral complex ions
70
How should you add the ammonia to the solution ?
- Dropwise
- So you can see all the observations
71
What do you see when you add ammonia drop wise to [Cu(H2O)6]2+ ?
- A pale blue precipitate of Cu(OH)2 is formed in the first stage of the reaction.
- The Cu(OH)2 precipitate then dissolves in excess ammonia to form a dark blue solution
72
What can be used as a source of chloride ions ?
HCl
73
What happens to [Cu(H2O)6]2+ when an excess of HCl is added ?
- The pale blue solution changes colour to form a yellow solution
- 6 ligands replaced with 4 ligands
74
What happens if water is added to the yellow [CuCl4]2- solution ?
- A blue solution will be formed
- It will be more dilute and paler than the original blue solution
75
What is the equation for [Cu(H2O)6]2+ reacting with excess chloride ?
- [Cu(H2O)6]2+ + 4Cl- → [CuCl4]2- + 6H2O
- Pale blue solution to yellow solution
- Octahedral to tetrahedral
76
When chlorine is added to [Cu(H2O)6]2+, why does it turn into tetrahedral ?
- This is because the chlorine ligands are larger in size than the water ligands, so fewer chloride ligands can fit around the central metal ion
- This explains the change in coordination number
77
What is formed when chromium (III) potassium sulphate is dissolved in water ?
[Cr(H2O)6]3+ ion is formed
78
What colour is the [Cr(H2O)6]3+ ion ?
Pale purple solution
79
What happens when chromium sulphate is dissolved in water ?
[Cr(H2O)5SO4]+ ion is formed
80
What colour is the [Cr(H2O)5SO4]+ ion ?
It is a green solution
81
What happens when [Cr(H2O)6]3+ reacts with an excess of ammonia ?
The [Cr(NH3)6]3+ ion is formed
82
What happens when [Cr(H2O)6]3+ reacts with an excess of ammonia (dropwise) ?
- Initially a grey-green precipitate of Cr(OH)3 is formed.
- The Cr(OH)3 precipitate dissolves in excess ammonia to form the complex ion [Cr(NH3)6]3+
83
What is the equation for the ligand substitution between [Cr(H2O)6]3+ and ammonia ?
- [Cr(H2O)6]3+ 6NH3 → [Cr(NH3)6]3+ + 6H2O
- Violet to purple colour change
84
What is a precipitation reaction ?
A precipitation reaction occurs when two aqueous solutions containing ions react together to form an insoluble ionic solid, called a precipitate.
85
How do copper, iron and manganese ions react with NaOH ?
They form precipitates
86
What does Cu2+ look like in aqueous solution ?
Blue solution
87
What does Fe2+ look like in aqueous solution ?
Pale green solution
88
What does Fe3+ look like in aqueous solution ?
Pale yellow solution
89
What does Mn2+ look like in aqueous solution ?
Pale pink solution
90
What does Cr3+ look like in aqueous solution ?
Violet solution
91
What happens when Cu2+ reacts drop wise with NH3 or NaOH ?
Blue precipitate is formed
92
What happens when Fe2+ reacts drop wise with NH3 or NaOH ?
- Green precipitate is formed
- Turns orange brown on standing
93
What happens when Fe3+ reacts drop wise with NH3 or NaOH ?
Orange brown precipitate
94
What happens when Mn2+ reacts drop wise with NH3 or NaOH ?
Light brown precipitate
95
What happens when Cr3+ reacts drop wise with NH3 or NaOH ?
Grey green precipitate
96
What happens when Cu2+ reacts with excess NH3 ?
Dissolves to form dark blue solution
97
What happens when Fe2+ reacts with excess NH3 ?
- Green precipitate is formed
- insoluble
98
What happens when Fe3+ reacts with excess NH3 ?
- Orange brown precipitate
- insoluble
99
What happens when Mn2+ reacts with excess NH3 ?
- Light brown precipitate
- insoluble
100
What happens when Cr3+ reacts with excess NH3 ?
Dissolves to form purple solution
101
What happens when Cu2+ reacts with excess NaOH ?
- Insoluble
- Cu(OH)2
102
What happens when Fe2+ reacts with excess NaOH ?
- Green precipitate is formed
- Insoluble
- Turns brown on standing
- Fe(OH)2
103
What happens when Fe3+ reacts with excess NaOH ?
- Orange brown precipitate
- Insoluble
- Fe(OH)3
104
What happens when Mn2+ reacts with excess NaOH ?
- Light brown precipitate
- Insoluble
- Mn(OH)2
105
What happens when Cr3+ reacts with excess NaOH ?
Dissolves to form dark green solution
