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C24 - Transition elements Flashcards

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1
Q

What are the d-block elements?

A

Located between groups 2 and 13 on the periodic table
Scandium to zinc - highest energy electron in 3d orbital

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2
Q

What are the physical properties of d-block elements?

A

Metallic
High melting point
High boiling point
Shiny
Conduct electricity and heat

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3
Q

What are some uses of d-block elements?

A

Coins
Construction
Electrical installation
Plumbing

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4
Q

What two transition elements do not follow the expected principle for electron configuration

A

Chromium and copper

Because half filled d5 and fully filled d10 provide stability

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5
Q

How do d block elements form ions

A

4s orbital empties before 3d orbitals

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6
Q

What are characteristic properties of transition metals + their compounds?

A

Form compounds where transition element has dif oxidation states

Form coloured compounds

Elements and their compounds act as catalysts

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7
Q

Trends in number of oxidation states in transition metals across the periodic table

A

Scandium to manganese- inc
Manganese to zinc - dec

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8
Q

What oxidation state do all transition metals have?

A

+2

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9
Q

How do different oxidation states present themselves in compounds

A

Different colours

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10
Q

Oxidation states and colours in transition metals

A
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11
Q

What is a catalyst

A

A substance that increases the rate of a chemical reaction without being used up itself
-provides alternate reaction pathway, lowering activation energy

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12
Q

Examples of transition metals as catalysts

A

Iron catalyst for Haber process
Vanadium (V) oxide, V2O5, catalyst for contact process
Nickel catalyst for hydrogenation
Manganese (IV) oxide, MnO2, catalyst for decomposition of H2O2

Fe2+ ions catalyse reaction of iodide ions and peroxodisulfate ions (S2O8 2-)

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13
Q

Formula of reaction of iodide ions and peroxodisulfate ions
(Observations with starch + Fe2+)

A

S2O8 2- + 2I- —> 2SO4 2- + I2

Blue black colour observed
Fe2+ makes colour appear faster

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14
Q

Equations showing how Fe2+ catalyses reaction of iodide ions and peroxodisulfate ions

A
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15
Q

What is a complex ion

A

Transition metal ion bonded to ligands by coordinate bonds

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16
Q

What is a ligand

A

Molecule/ion that can donate a pair of electrons to the central transition metal ion forming a coordinate bond

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17
Q

What is a coordinate bond

A

Shared pair of electrons in which the bonded pair have been provided by only one of the bonding atoms

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18
Q

What is the coordination number

A

Total number of coordinate bonds formed between a central metal ion and ligands

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19
Q

How was complex ions written?

A
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20
Q

What is a monodentate ligand?

A

A ligand that can donate one lone pair of electrons to a central metal ion

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21
Q

What is a bidentate ligand?

A

A ligand that can donate two lone pairs of electrons to a central metal ion

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22
Q

What is the shape of six coordinate complexes?

A

Octahedral
Bond angle - 90

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23
Q

What is the shape of four coordinate complexes

A

Tetrahedral
Bond angle 109.5

Square planar
Bond angle 90
(Occurs in transition metals with 8 d-electrons in higher energy d-subshell)

Pd(II), Pt(II), and Au(III)

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24
Q

What is stereoisomerism

A

Same structural formula but different arrangement of atoms in space

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25
What are the two types of stereoisomerism
Cis-trans and optical
26
How is isomerism presented in complex ions
Cis trans - Square planar Octahedral with 2 ligands of one type and 4 of another Optical - (octahedral w bidentate) Octahedral complexes with 3 bidentate ligands Octahedral complexes with 2 bidentate and 2 monodentate Octahedral complexes with 1 bidentate and 2 different monodentate ligands
27
How does cis trans isomerism occur in square planar complexes eg, [Pd(NH3)2Cl2]
28
How does dis trans isomerism occur is octahedral complexes with monodentate ligands eg. [Co(NH3)4Cl2]+
29
How does dis trans isomerism occur is octahedral complexes with bidentate ligands eg. [Co(NH2CH2CH2NH2)2Cl2]+
30
Optical isomerism in octahedral complexes Eg. [Co(NH2CH2CH2NH2)2Cl2]+
31
What is a ligand substitution reaction
A reaction in which one/more ligands in a complex ion are replaced by different ions
32
What happens when excess ammonia is added to [Cu(H2O)6]2+ (equations)
Pale blue turns to dark blue
33
What will you see in the dropwise addition of ammonia to [Cu(H2O)6]2+
1) Pale blue precipitate of Cu(OH)2 formed 2) Cu(OH)2 dissolves in excess ammonia to form dark blue solution
34
What happens when concentrated HCl is added to [Cu(H2O)6]2+
Pale blue solution to yellow solution (If water added, it turns back to blue but paler and more dilute)
35
When HCl is added to [Cu(H2O)6]2+ what changes are seen in the coordination number? and the oxidation state of copper?
Coordination number changes from 6 to 4 Oxidation number of copper remains at +2
36
What is formed when hydrated chromium (III) potassium sulphate diolves in water
Pale purple solution [Cr(H2O)6]3+
37
How does ligand substitution occur in haemoglobin
RBC made of 4 protein chains Each protein chain has 1 central haem group Haem group has centra metal ion Fe2+ which can bind to O2 (forming oxyhaemoglobin) Can also bind to CO2 similarly -CO can irreversibly bind to Fe2+ forming carboxyhaemoglobin -Occurs through ligand substitution -CO bonds more strongly to Fe2+
38
What is a precipitation reaction?
Formation of an insoluble solid from a solution during a chemical reaction (usually from two aqueous reactants)
39
How do transition metals react with NaOH
Form precipitates
40
How does iron (II) hydroxide react with air + equation
Green to brown
41
Describe a precipitation reaction for copper (first stage of ammonia reaction)
Cu(OH)2 is blue precipitate Dissolves with ammonia to form deep blue solution [Cu(NH3)4(H2O)2]2+
42
Describe a precipitation reaction of chromium (first stage of reaction with ammonia)
Cr(OH)3 is green precipitate which dissolves in excess ammonia to form [Cr(NH3)6]3+ which is purple solution
43
What is cis-platin?
Used as cancer treatments Attacks tumours, enabling them to shrink in size Forms platinum complex inside cell which binds to DNA preventing it from replicating, activation of cells repair mechanism leads to apoptosis Has negative side effects including kidney damage
44
Describe the oxidation of Fe2+ to Fe3+
Use MnO4- in acidic conditions Fe2+ oxidised to Fe3+ MnO4- (purple) reduced to Mn2+ Purple to colourless
45
Describe reduction of Fe3+ to Fe2+
Use I- ions Orange brown Fe3+ reduced to pale green Fe2+ I- oxidised to I2
46
How can standard electrode potentials explain the reactions of Fe2+ and MnO4-
E for MnO4-/Mn2+ is more +ve than Fe3+/Fe2+ SO Fe2+ oxidised and MnO4- reduced
47
How can standard electrode potentials explain the reactions of Fe3+ and I-
E for Fe3+/Fe2+ more +ve than I2/I- SO I- oxidised and Fe3+ reduced
48
Describe the reduction of Cr2O7 2- to Cr3+
Use zinc Orange Cr2O7 2- reduced to green Cr3+ Zinc oxidised to Zn2+ Excess zinc can further reduce Cr3+ to pale blue Cr2+
49
Describe the oxidation of Cr3+ to CrO4 2-
Use hot alkaline H2O2 Cr3+ oxidised to CrO4 2- Oxygen in H2O2 reduced
50
Describe the reduction of Cu2+ to Cu
Excess I- I- oxidised to brown I2 Cu2+ reduced to Cu+
51
What happens when solid Cu2O reacts with hot dilute sulfuric acid
Forms brown precipitate of copper And blue solution of copper (II) sulfate Cu+ oxidised and reduced Disproportionation
52
How do you identify transition metals
Precipitate reactions with aqueous NaOH
53
How do you identify NH4+
Heat with NaOH, should produce ammonia gas Damp red litmus paper should turn blue
54
Tests to identify anions
55
K (19) electron config
[Ar] 4s^1
56
Ca (20) electron config
[Ar] 4s^2
57
Sc (21) electron config
[Ar] 3d^1 4s^2
58
Ti (22) electron config
[Ar] 3d^2 4s^2
59
V (23) electron config
[Ar] 3d^3 4s^2
60
Co (27) electron config
[Ar] 3d^7 4s^2
61
Mn (25) electron config
[Ar] 3d^5 4s^2
62
Cr (24) electron config
[Ar] 3d^5 4s^1
63
Fe (26) electron config
[Ar] 3d^6 4s^2
64
Ni (28) electron config
[Ar] 3d^8 4s^2
65
Cu (29) electron config
[Ar] 3d^10 4s^1
66
Zn (30) electron config
[Ar] 3d^10 4s^2
67
Colour of Cr 3+
Green BUT violet when surrounded by 6 water molecules
68
Colour of Cr2O7 2-
Orange
69
Colour of Mn 2+
Pale pink
70
colour of MnO4 2-
Green
71
Colour of MnO4 -
purple
72
Colour of Fe 2+
Pale green
73
Colour of Fe 3+
yellow
74
Colour of Cu 2+
Blue
75
Why do transition metals make good catalysts
Have surfaces that allow substances to adsorb lowering activation energy of reaction
76
Cu 2+ in aq solution
[Cu(H2O)6] 2+ (aq) Cu 2+ Blue
77
Fe 2+ in aq solution
[Fe(H2O)6] 2+ (aq) Fe 2+ Pale green
78
Fe 3+ in aq solution
[Fe(H2O)6] 3+ (aq) Fe 3+ Yellow
79
Mn 2+ in aq solution
[Mn(H2O)6] 2+ (aq) Fe 3+ Pale pink
80
Cr 3+ in aq solution
[Cr(H2O)6] 3+ (aq) Cr 3+ Green
81
What happens when you as OH or NH3 to aq Cu 2+ (+excess OH- / +excess NH3)
Cu(OH)2(H2O)4 (s) Pale Blue Precipitate OH- : insoluble no change NH3 : [Cu(NH3)4(H2O2)2]2+ (aq) - dark blue solution
82
What happens when you as OH or NH3 to aq Fe 2+ (+excess OH- / +excess NH3)
Fe(OH)2(H2O)4 (s) Green Precipitate OH- : insoluble no change NH3 : Insoluble, no change
83
What happens when you as OH or NH3 to aq Fe 3+ (+excess OH- / +excess NH3)
Fe(OH)3(H2O)3 (s) Orange-brown Precipitate OH- : insoluble no change NH3 : Insoluble, no change
84
What happens when you as OH or NH3 to aq Mn 2+ (+excess OH- / +excess NH3)
Mn(OH)2(H2O)4 (s) Pink Precipitate (turns brown in air) OH- : insoluble no change NH3 : Insoluble, no change
85
What happens when you as OH or NH3 to aq Cr 3+ (+excess OH- / +excess NH3)
Cr(OH)3(H2O) (s) Green-grey Precipitate OH- : soluble, dark green solution Cr(OH)6 3- NH3 : Cr(NH3)6 3+ (aq) purple solution
86
Ligand substitution of Cl- into Fe 3+, Co 2+ and Cu 2+
87
What is a hexa aqua complex
Metal ion joined to 6 water molecules with coordinate bonds
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