1
Q
Describe D block elements?
A
- All metallic
- High melting points
- High boiling points
- Shiny in appearance
- Conduct both electricity and heat
2
Q
What is a transition element?
A
d block elements that form at least one ion with a partially filled d-orbital (scandium and zinc not true transition elements as they have empty or full d orbitals)
3
Q
What is the electronic configuration of Titanium?
A
[Ar] 4s2 3d2
4
Q
What is the electronic configuration of Vanadium?
A
[Ar] 4s2 3d3
5
Q
What is the electronic configuration of Chromium?
A
[Ar] 4s1 3d5
6
Q
What is the electronic configuration of Manganese?
A
[Ar] 4s2 3d5
7
Q
What is the electronic configuration of iron?
A
[Ar] 4s2 3d6
8
Q
What is the electronic configuration of cobalt?
A
[Ar] 4s2 3d7
9
Q
What is the electronic configuration of nickel?
A
[Ar] 4s2 3d8
10
Q
What is the electronic configuration of copper?
A
[Ar] 4s1 3d10
11
Q
What is the electronic configuration of zinc?
A
[Ar] 4s2 3d10
12
Q
What is the electronic configuration of Fe2+?
A
[Ar] 4s0 3d6
13
Q
What is the electronic configuration of Fe3+?
A
[Ar] 4s0 3d5
14
Q
What is the electronic configuration of Sc3+?
A
[Ar]
15
Q
What is the electronic configuration of Zn2+
A
[Ar] 4s0 3d10
16
Q
What is the electronic configuration of V3+?
A
[Ar] 4s0 3d2
17
Q
What is the electronic configuration of Mn7+?
A
[Ar]
18
Q
What is the electronic configuration of Scandium?
A
[Ar] 4s2 3d1
19
Q
What is the electronic configuration of Cu+?
A
[Ar] 4s0 3d10
20
Q
What is the electronic configuration of Mn2+?
A
[Ar] 4s0 3d5
21
Q
What is the electronic configuration of Ti3+?
A
[Ar] 4s0 3d1
22
Q
What are the properties of transition elements?
A
- They form compounds in which the transition element has different oxidation states
- They form coloured compounds
- The elements and their compounds can act as catalysts
23
Q
When are transition metals used as catalysts?
A
- The Haber Process (manufacture of ammonia), iron catalyst
- Contact Process (production of sulphur dioxide from the oxidation of sulphur dioxide, vanadium (V) oxide catalys
- Hydrogenation of alkenes (vegetable fats) (to make margarine), nickel catalyst
- Catalytic decomposition of hydrogen peroxide forming oxygen and manganese oxide as catalyst
- Iodine and thiosulfate (Fe2+ catalyst) and homogenous catalyst
24
Q
Why 4s and 3d trouble?
A
4s and 3d is very close so energy to promote is less than stability gained from a half filled shell
25
Why are coloured compounds formed?
- Compounds containing transition elements form are coloured as solids and in aqueous solution
- The colour is linked to the energy levels of the d orbitals which depend on the charge on the metal ion and the ligands involved
- E.G. potassium dichromate (VI) is bright orange, cobalt (II) chloride is pink purple, nickel (II) sulcate is green whilst hydrated copper (II) sulfate is blue
26
Why do transition elements have multiple oxidation states?
- Transition elements form compounds with multiple oxidation states
- All transition elements have an oxidations Tate of +2
- Manganese has the most possible oxidation states, +2 through to +7
27
What is a complex ion?
A central metal ion surround by ligands
28
What is a ligand?
A molecule or ion that donates a pair of electrons to a central metal ion via a covalent bond
29
What is a coordinate bond?
A covalent bond when Bothe electrons in the shared pair of electrons come from the same atom (a dative bond outside of transition metals)
30
What is coordination number?
The number of coordinate bonds attached to the metal ion
31
What is a mono dentate ligand?
- Only one lone pair in each ligand
| - A ligand that is able to donate one pair of electrons to a central metal ion
32
What is a bidentate ligand?
- Two lone pairs in each ligand
| - A ligand that donates two pairs of electron to then central metal ion, forming two coordinate bonds
33
What is a hexadentate ligand?
Six lone pairs in each ligand
34
What is a stereoisomer?
The same molecular/structural formula but a different arrangement of atoms in space
35
Describe cis-trans isomerism
1. Complexes with a coordination number of 4 and a square planar shape
2. Complexes with a coronation number of 6 that contain four of one ligand and two of another
3, Complexes with a coordination number of 6 that contain two bidentate ligands and two mono dentate ligand
36
What are catalyst and why are transition metals suitable?
- Catalyts increase the rate of reaction without being changed themselves
- The ability to change oxidation state makes transition elements excellent catalysts
37
What are the two most common bidentate ligands?
1. 1,2-diminoethane (frequently shortened to en)
| 2. Ethanedioate (oxalate) ion
38
What happens in the 1,2-diminoethane?
Each nitrogen atom donates a pair of electrons to the central metal ion forming a coordinate bond
39
What happens in ethanedioate ion?
Each negatively charged oxygen atom donates a lone pair of electrons to the central metal ion
40
What does the type of stereoisomerism for complex ions depend on?
- The number and type of ligands that are attached tot he central metal ion and the shape of the complex
1. Some four-coordinate and six-coordinate complex ions containing two different mono dentate ligands show cis-trans isomerism
2. Soem six-coordinate complex ions containing mon-dentate and bidentate ligands can show both cis-trans and optical isomerism
41
What does cis-trans isomerism need?
1. Presence of a C=C bond which prevents rotation of groups attached to each carbon atom of the C=C bond
2. In compels ions, no double bonds is involved and the shame if the complex holds groups in different orientations about the central metal ion
3. It occurs on some square planar and octahedral shapes
42
In square planar what is the cis and trans isomers?
- The lianas are arranged int he same plane at the corner of a square with 90 degree bond angles
1. Cis: the two identical groups are adjacent to each other (coordinate bonds between identical ligands are 90 degrees)
2. Trans: the two identical groups are opposite each other (coordinate bonds between identical ligands are 180 degrees)
43
In octahedral with mondentate ligands what are the cis and trans isomer?
- Containing four of one type of ligand and two of another type
1. Cis: Two chloride ligands are adjacent to each other with their coordinate bond spotted by 90 degrees (violet)
2. Trans: Two chloride ligands are at opposite corners of the octahedron, with their coordinate bonds 180 degrees apart (Green)
44
When does optical isomerism occur?
1. Octahedral complexes
2. Complexes with a coordination number of 6 that contain two bidentate ligands and two mono dentate ligands, Optical isomerism applies to the cis isomer only
3. Complexes with a coordination number of 6 that contain three bidetnate ligands
4. Complexes with a coordination number of 6 that contain hexadentate ligands
45
What are optical isomers?
Called enantiomers are non-superimposable mirror images of each other, like a left hand and a right hand
46
Why can trans-isomers not form optical isomers?
As a mirror image is exactly the same and can be super imposed
47
What is a ligand substitution reaction?
One in which one ligand in a complex ion is replaced by another ligand
48
Describe the reaction of ligand substitution with ammonia
- When an excess of aqueous ammonia is added to a solution containing [Cu(H2O)6]2+
- The pale blue solution changes to form a dark blue solution
- A pale blue precipitate of Cu(OH)2 is formed in the first stage of the reaction and then the Cu(OH)2 precipitate dissolves in excess ammonia to from a dark blue solution
- Fro full reaction a to c need excess ammonia
49
Describe the ligand substitution with chloride ions
- Concentrated HCL can be used a s a source of chloride ions
- Excess HCL added to [Cu(H2O)6]2+
- Pale blue solution changes to a yellow colour
- Six water ligands have been replaced by four chloride ligands
- During experiment an intermediate green solution is formed as a result of the yellow solution missing with the blue solution to give a green colour as the reaction proceeds
50
What happens if you add water to the yellow solution?
-A blue solution ill be formed, although more dilute and paler in colour than the original blue solution
51
In ligand substitution with chloride ions what changes and why?
1. Coordination number and colour changes and shape from octahedral to tetrahedral
2. Oxidation number fo copper remains as 2+
3. Chloride ligands are larger in size than the water ligands, so fewer chloride ligands can dir around the central Cu2+ ion and this explains the change in coordination number (large ionic radius Cl-)
52
Describe ligand substitution with aqueous chromium (II) ions and NH3
1. NH3: Violet solution to grey-green precipitate
2. Excess ammonia NH3: [Cr(NH3)6]3+ is formed
3. When added drop wise to the chromium (III) solution:
- Initially a grey-green precipitate of Cr(OH)3 is formed
- The Cr(OH)3 precipitate dissolves in excess ammonia to from the complex ion [Cr(NH3)6]3+
53
What are the different types of Chromium?
1. When chromium (III) potassium sulcate, KCr(SO4)2.12(H2O) is dissolved in water, the complex ion [Cr(H2O)6]3+ is formed (pale purple solution)
2. When chromium (III) sulfate is dissolved in water, a green solution containing chromium (III) is formed, however this solution is NOT [Cr(H2O)6]3+, but instead the complex ion [Cr(H2O5SO4]+, where one of the water ligand has been replaced by the sulfate ion SO42-
3. Both the purple and green solutions contain chromium (III) ions in oxidation states +3
54
What is haemoglobin?
- Haemoglobin is a complex protein contain 4 polypeptide chains. Each chain contains 4 non-protein components called harm groups that have a central Fe2+ ion
- As blood passes through the lungs the iron in the ham group bind to oxygen and transports it around the body
55
Describe the structure of the haemoglobin?
- Coordination number: 6
- 4 bonds to nitrogen atoms in harm
- 1 bond to globin (via a histidine side chain)
- 1 open site to bind to oxygen
56
How can carbon monoxide kill?
- CO can also bind to the Fe (II) in the haem group, forming carboxyhaemoglobin rather than oxyhaemoglobin
- CO bind harm more strongly than O2. If CO is inhaled then ligand substitution occurs and CO binds strongly and irreversibly
- If the CO level in the lungs is too high, oxygen transport is prevented
57
What is a precipitation reaction?
A precipitation reaction occurs when two aqueous solutions containing ions react to from an insoluble ionic solid, called a precipitate
58
What happens with Cu2+ and aqueous NaOH?
1. Blue solution reacts to from a blue precipitate of copper (II) hydroxide
2. The precipitate is insoluble in excess sodium hydroxide
59
What happens with Fe2+ and aqueous NaOH?
1. Pale green solution reacts to form a green precipitate of iron (II) hydroxide
2. The precipitate is insoluble in excess sodium hydroxide but turns brown at its surface on staging in air as iron (II) is oxidised to iron (III)
60
What happens with Fe3+ and aqueous NaOH?
1. Pale yellow solution reacts to form an orange-brown precipitate of iron (III) hydroxide
2. The precipitate is insoluble is excess sodium hydroxide
61
What happens with Mn2+ and aqueous NaOH?
1. Pale pink solution reacts to form a light brown precipitate of manganese (II) hydroxide which darkens on standing in air
2. The precipitate is insoluble in excess sodium hydroxide
62
What happens with Cr3+ and aqueous NaOH?
1. Violet solution reacts to from a grey-green precipitate of chromium (III) hydroxide
2. The precipitate is soluble in excess sodium hydroxide forming a dark green solution
63
How does Fe2+, Fe3+ and Mn2+ react with excess of aqueous ammonia?
- The same way as they react with aqueous sodium hydroxide, forming precipitate of Fe(OH)2(s), Fe(OH)3(s), and Mn(OH)2 (s)
- There is no further reaction with aqueous ammonia and so these precipitates do not dissolve
64
What are the colours of the solution of transition metals?
- The solid compounds can be dissolved in water to produce coloured solutions
- The colour of a solution is linked to the partially filled d orgbals of the transition metal ion
- The colour of a solution can vary with different oxidation states
- Iron (II) pale green
- Iron (III) yellow
- Cr (III) green
- Cr (VI) yellow or orange
65
What is cis-platin and why is it important?
1. Cis-platin is a drag used in many cancer treatments
2. It is the cis isomer of [PtCl2(NH3)2]
3. Cis-platin undergoes hydrolysis at the tumour site and the resulting free platinum ions bind to DNA and prevent transcription
4. Carbo-platin has been developed more recently to prevent side effects
66
Describe the reduction of Cu2+ to Cu+
- When aqueous copper (II) ions, Cu2+ react with EXCESS iodide ions, I- (aq), a redox reaction occurs
1. I- is oxidised to I2
2. Cu2+ is reduced to Cu+
3. The Cu+ forms a white precipitate of copper (II) iodide
67
What is the disproportionation of Cu+ ions?
1. When solid copper (I) oxide, Cu2O reacts with hot dilute sulphuric acid, a brown precipitate of copper is formed with a blue solution of copper (II) sulphate
2. In this reaction copper (I) ions, Cu+ have been simultaneously oxidised and reduced
3. As the same element has been reduced and oxidised this reaction is disproportionation
- Reduction to Cu
- Oxidation to CuSO4
68
What is true about Pt(NH3)Cl2?
-One of its stereoisomers is used as an anticancer drug
69
How does ligand substitution allow haemoglobin to transport oxygen in the blood?
1. Oxygen bonds to Fe 2+
| 2. When required O2 substituted or O2 released
70
Describe bonding in platin
- Ligand donates an electron pair to metal ion (pt2+)
| - Forms a coordinate bond to the metal ion
71
What is the action of platin?
-Binds to DNA of cancer cells or stops cancer cells from dividing/replicating
Z A Level Chemistry
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