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A-level chemistry year 2 > Transition Metals > Flashcards

Transition Metals Flashcards

1
Q

Define a transition metal

A

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

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2
Q

What does it mean to show variable oxidation numbers

A
  • transition metals forming multiple stable ions
  • each ion the transition metal has a different oxidation number (e.g. vanadium has four stable oxidation numbers)
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3
Q

name 4 properties of transition metals

A
  • variable oxidation numbers
  • form complex ions
  • ions are often coloured in solution
  • act as good catalysts
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4
Q

why do transition metals show variable oxidation numbers

A
  • transition metals form ions by removing electrons from both their 3d and 4s subshells
  • these subshells are of similar energy levels
  • so similar successive ionisation energies
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5
Q

what is a complex ion

A

central metal ion surrounded by dative covalently bonded ligands

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6
Q

what is a ligand

A

an atom, ion or molecule that donates a pair of electrons to a central metal atom or ion (forms a dative covalent bond)

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7
Q

name and define the three types of ligands

A
  • monodentate –> ligands with one lone pair of e-
  • bidentate –> ligands with two lone pairs of e- and can form two dative covalent bonds with the metal ion
  • multidentate –> ligands with 2 or more lone pairs of e-
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8
Q

given an example of a bidentate ligand

A

1,2-diaminoethane
NH2CH2CH2NH2

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9
Q

Give an example of a multidentate ligand

A

EDTA4-
(hexadentate ligand)

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10
Q

give an example of a multidentate ligand in the body

A
  • Haemoglobin an iron II complex containing multidentate ligand called a Haem group
  • Haem group made up of a ring containing 4 N atoms ( can form 4 dative covalent bonds with Iron II )
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11
Q

define coordination number

A

number of dative covalent bonds formed with the central metal ion

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12
Q

what shape do six-fold coordination complexes have

A

octahedral

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13
Q

why do complexes with different coordination numbers have distinct shapes

A
  • bonding electrons of the dative covalent bonds repel each other
  • so ligands positioned as far away from each other as possible
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14
Q

what shape do four-fold coordination complexes have

A

tetrahedral

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15
Q

what ligand generally forms four-fold complexes

A

Cl- (large ligand)

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16
Q

most common shapes of coordination complexes

A
  • octahedral
  • tetrahedral
  • square planar
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17
Q

what type of complex ions display what type of isomerism

A
  • tetrahedral + square planar
  • Cis/trans
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18
Q

what is used as a drug for cancer and what do you need to look out for with this drug

A
  • cis-platin (a complex of platinum II)
  • trans-platin is toxic, so must ensure only cis-platin is given to patients
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19
Q
A
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20
Q

What happens when ligands bond to transition ions

A

3d orbitals are split Into 2 different energy levels

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21
Q

What does the size of the energy gap between split 3d orbitals indicate

A

The frequency of light absorbed

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22
Q

What factors influence the amount of energy needed to make electrons jump up to the higher 3d energy levels

A

Of the central metal ion:
- oxidation number
- ligands
- coordination number

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23
Q

What causes complex ions/aqueous ions to display a specific colour

A
  • ligand binding results in 3d orbitals splitting to different energy levels
  • difference in energy level determines frequency of light absorbed
  • light frequency not absorbed is transmitted or reflected, and combine to make the colour that is displayed
24
Q

What causes a compound to look white or colourless

A
  • no 3d electrons/ 3d sub hell is full
  • no electrons jump, no energy is absorbed, so no frequency of light absorbed
25
Q

Vanadium +5 ion + colour

A
  • VO2^+
  • Yellow
26
Q

Vanadium +4 ion + colour

A
  • VO^2+
  • Blue
27
Q

Vanadium +3 ion + colour

A
  • V3+
  • green
28
Q

Vanadium +2 ion + colour

A
  • V2+
  • violet
29
Q

Chromium +6 ion + colour

A
  • Cr2O7^2-
  • orange
30
Q

Chromium +3 ion + colour

A
  • Cr3+
  • green
31
Q

Iron +3 ion + colour

A
  • Fe3+
  • yellow
32
Q

Iron +2 ion + colour

A
  • Fe2+
  • pale green
33
Q

Cobalt +2 ion + colour

A
  • Co2+
  • pink
34
Q

Copper +3 ion + colour

A
  • Cu2+
  • pale blue
35
Q

What is ligand exchange

A

One ligand swapped for another ligand

36
Q

What happens to the complex ion if ligand exchange occurs on ligands of similar size

A
  • coordination number of complex ion is the same
  • shape is the same
37
Q

What happens to the complex ion if ligand exchange reaction occurs with ligands different in size

A
  • change in coordination number and change of shape
38
Q

[Cr(H2O)6]3+ (aq) + 6NH3(aq) <=>

A

[Cr(NH3)6]3+ (aq) + 6H2O(l)
- colour change green-purple
- octahedral shape - octahedral shape

39
Q

[Co(H2O)6]2+ (aq) + 4Cl- (aq) <=>

A

[CoCl4]2- (aq) + 6H2O(l)
- colour change pale pink to blue
- octahedral to tetrahedral shape

40
Q

[Cu(H2O)6]2+ (aq) + 4NH3(aq) <=>

A

[Cu(NH3)4(H2O)2]2+ (aq) + 4H2O
- colour change pale blue to deep blue
- octahedral to octahedral shape
(partial ligand substitution)

41
Q

[Cu(H2O)6]2+ (aq) + 4Cl- <=>

A

[CuCl4]2- (aq) + 6H2O(l)
- colour change pale blue to yellow
- octahedral to tetrahedral shape

42
Q

Precipitate reactions:
[Cu(H2O)6]2+ (aq)
—> + OH-
—> + NH3 (not excess)

A

—> [Cu(H2O)6]2+ (aq) + 2OH- (aq) —> Cu(OH)2(H2O)4 + 2H2O
—> [Cu(H2O)6]2+ (aq) + 2NH3 (aq) —>Cu(OH)2(H2O)4 + 2NH4+ (aq)
Pale blue solution - blue precipitate

43
Q

Precipitate reactions:
[Fe(H2O)6]2+ (aq)
—> + OH-
—> + NH3

A

—> [Fe(H2O)6]2+ (aq) + 2OH- (aq) —> Fe(OH)2(H2O)4 + 2H2O(l)
—> [Fe(H2O)6]2+ (aq) + 2NH3 (aq) —>Fe(OH)2(H2O)4 + 2NH4+ (aq)
Pale green solution - green precipitate
Green precipitate darkens on standing (is oxidised to Iron(III) hydroxide)

44
Q

Precipitate reactions:
[Fe(H2O)6]3+ (aq)
—> + OH-
—> + NH3

A

—> [Fe(H2O)6]3+ (aq) + 3OH- (aq) —> Fe(OH)3(H2O)3 + 3H2O(l)
—> [Fe(H2O)6]3+ (aq) + 3NH3 (aq) —> Fe(OH)3(H2O)3 + 3NH4+ (aq)
Yellow solution - orange precipitate
Orange precipitate darkens on standing

45
Q

Precipitate reactions:
[Co(H2O)6]2+ (aq)
—> + OH-
—> + NH3 (not excess)

A

—> [Co(H2O)6]2+ (aq) + 2OH- (aq) —> Co(OH)2(H2O)4 + 2H2O(l)
—> [Co(H2O)6]2+ (aq) + 2NH3 (aq) —> Co(OH)2(H2O)4 + 2NH4+ (aq)
Pale pink solution - blue precipitate
Blue precipitate turns brown on standing

46
Q

Precipitate reactions:
Co(OH)2(H2O)4
—> + NH3 (excess)

A

—> Co(OH)2(H2O)4 + 6NH3(aq) —> [Co(NH3)6]2+ (aq) + 2OH- (aq) + 4H2O(l)
blue precipitate dissolves to form a yellow-brown solution

47
Q

Why are transition metals good catalysts

A
  • they change oxidation number by gaining or losing electrons within their d-orbitals
  • so can transfer electrons to speed up reactions
48
Q

What is the contact process and what acts as a catalyst

A
  • SO2 is oxidised to SO3
  • V2O5 (Vanadium (V) oxide) acts as a catalyst
49
Q

Reactions within contact process

A

—> Vanadium oxidises SO2 to SO3
V2O5 + SO2 —> SO3 + V2O4 (Vanadium (V) to Vanadium (IV))
—> Vanadium (IV) oxide then reduced back to original state
V2O4 - 1/2O2 —> V2O5

50
Q

Describe how a catalytic converter works (heterogeneous catalyst)

A
  • adsorption of reactant molecules onto the surface of the catalyst
  • weakening of bonds between the reactants atoms + activation of the molecules so they react more easily
  • desorption of product molecules from the catalyst
51
Q

What is a homogenous catalyst and how does it work

A
  • a catalyst in the same phase as the reactants
  • combines the reactants to form an intermediate species, which will then react to form the products and reform the catalyst
52
Q

What catalyst is used in peroxodisulfate ions oxidising iodide ions + why is the reaction without the catalyst slow

A
  • Fe2+
  • both ions negatively charged so they repel each other and are unlikely to collide and react
53
Q

Peroxodisulfate ions oxidising iodide ions + Fe2+ catalyst reactions

A

S2O82- (aq) + 2Fe2+ (aq) —> 2Fe3+ (aq) + 2SO4-2 (aq) ((Fe2+ oxidised))
2Fe3+ (aq) + 2I- (aq) —> I2 (aq) + 2Fe2+ (aq) ((Fe2+ is regenerated))

54
Q

What is an autocatalyst

A
  • catalyst is a product of the reaction and acts as a catalyst for the reaction
  • reaction progresses, amount of product increases, reaction rate increases
55
Q

Give an example of an autocatalyst

A

Mn2+

56
Q

All reactions with MnO4- + C2O42-

A

—> 2MnO4- (aq) + 16H+ (aq) + 5C2O4^2- (aq) —> 2Mn2+ (aq) + 8H2O(l) + 10CO2(g)
- 4Mn2+ (aq) + MnO4- (aq) + 8H+ (aq) —> 5Mn3+ (aq) + 4H2O(l)
- 2Mn3+ (aq) + C2O4^2- (aq) —> 2Mn2+ (aq) + 2CO2(g)

A-level chemistry year 2 (8 decks)

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