Transition Metals Flashcards

1
Q

What is a transition metal?

A

A metal that can form one or more stable ions with an incomplete sub-shell.

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2
Q

Write the electronic configuration of Ti, V, Cr, Mn, Fe, Co, Ni and Cu?

A
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3
Q

How are electrons lost from trasition metal atoms to form ions?

A

Electrons are lost from the 4s subshell first as the 4s subshell is higher in energy.

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4
Q

Write the electronic configuration of Fe 2+, Fe 3+ and Mn 2+ ions.

A
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5
Q

Why is scandium not a transition metal?

A

It can only form one stable ion Sc 3+ and it does not have an incomplete sub-shell.

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6
Q

Why is zinc not a transition metal?

A

It can only form one stable ion Zn 2+ and it does not have an incomplete sub-shell.

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7
Q

What are the physical properties of transition metals?

A

They have a high density. They have high melting and boiling points.

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8
Q

What are the chemical properties of transition metals?

A
  1. They can form complex ions.
  2. They form coloured ions.
  3. They are good catalysts.
  4. They have varying oxidation states.
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9
Q

What is a complex ion?

A

A metal ion is coordinately bonded to many ligands.

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10
Q

What is a ligand?

A

An atom, ion or molecule that can donate a pair of electrons.

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11
Q

What are monodentate ligands?

A

Ligands that can donate only one pair of electrons and form one coordinate bond with the central metal ion.

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12
Q

What are examples of monodentate ligands?

A

Ammonia. water and chloride ions.

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13
Q

What are bidentate ligands?

A

Ligands that can donate two pairs of electrons and form two coordinate bonds with the central metal ion.

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14
Q

What are examples of bidentate ligands?

A

ethane-1,2-diamine

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15
Q

What are multidentate ligands?

A

Ligands that can donate more than two pairs of electrons and form more than two coordinate bonds with the central metal ion.

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16
Q

What are examples of multidentate ligands?

A

EDTA 4- forms 6 coordinate bonds.

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17
Q

What shape are the complex ions when there are 6 coordinate bonds?

A

octahedral

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18
Q

What shape are the complex ions when there are 6 coordinate bonds?

A
  1. Tetrahedral.
  2. Square planar.
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19
Q

What are stereoisomers?

A

Compounds that have the same molecular formula but a different arrangement of atoms within a space.

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20
Q

What are optical isomers?

A

Isomers that are mirror images of each other and are non-superimposable.

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21
Q

Where does optical isomerism happen in complex ions?

A

When three bidentate ligands bind to the central metal ion.

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22
Q

Where does E-Z isomerism happen in complex ions?

A
  1. When 4 monodentate ligands bind to the central metal ion.
  2. Octahedral complex ions that 4 of the same ligands and 2 different ligands bound to the central metal ion.
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23
Q

What is the structure of cisplatin?

A
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24
Q

How do different energy levels form in the 3d-subshell?

A

When the ligands bond to the ions some orbitals gain more energy than others and that splits the subshell into different energy levels.

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25
Q

How do electrons jump up energy levels?

A

They need to absorb energy equal to the energy gap which they get from visible light.

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26
Q

Why do transition metals form coloured compounds?

A

When visible light hits a transition metal ion some frequencies are absorbed so the electrons can jump up an energy level. The rest of the frequencies are reflected and combined to make the complementary colour of the absorbed frequencies.

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27
Q

Why are some compounds colourless?

A

They have no 3d electrons or their 3d subshell is full meaning that no electrons will jump up an energy level and no energy will be absorbed. Since all frequencies of light are reflected the compound appears white or colourless.

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28
Q

What can cause a change in colour in a transition metal?

A
  1. Change in oxidation state.
  2. Change in coordination number.
  3. Change in ligand.
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29
Q

What is the colour change when you go from [Fe(H2O)6]2+ to [Fe(H2O)6]3+?

A

pale green to yellow

30
Q

What is the colour change when you go from [V(H2O)6]2+ to [V(H2O)6]3+?

A

violet to green

31
Q

What is the colour change when you go from [Cu(H2O)6]2+ to [CuCl4]2-?

A

blue to yellow

32
Q

What is the colour change when you go from [Co(H2O)6]2+ to [Co(NH3)6]2+?

A

pink to straw-coloured

33
Q

What is the purpose of colorimetry?

A

It can be used to determine the concentration of a solution by measuring how much light it absorbs.

34
Q

How does colorimetry work?

A

White light is shone through a filter which only lets the colour that the sample absorbs through. The light then passes into a colorimeter which shows how much light was absorbed by the sample. The more light absorbed by the sample the more concentrated the coloured solution is.

35
Q

What are the axis of the calibration curve in colorimetry?

A

Relative absorbance on the y-axis. Concentration on the x-axis.

36
Q

Why is there no change in the shape and coordination number of a complex ion when water and ammonia ligands are substituted?

A

They have a similar size and are both uncharged.

37
Q

Why is there a change in the shape and coordination number of a complex ion when water and chlorine ligands are substituted?

A

The chlorine ions are larger compared to the water ligands meaning that less of them can fit around the metal ion. This changes the shape from octahedral to tetrahedral and the coordination number from 2+ to 2-.

38
Q

What is the equation for the partial substitution of ammonia into [Cu(H2O)6]2+

A
39
Q

Draw the haem group in haemoglobin. Label the porphyrin ligand.

A
40
Q

How does the haem group take the blood around the body?

A

In the lungs where the oxygen concentration is high, the water ligands are substituted for oxygen molecules to form oxyhaemoglobin. When the oxyhaemoglobin gets to the part of the body where oxygen is needed the opposite happens and the oxygen is released.

41
Q

How does carbon monoxide poisoning occur?

A

The carbon monoxide substitutes the water ligands and since it forms a very strong bond it does not readily exchange with oxygen and water ligands meaning the haemoglobin can no longer transport oxygen around the body.

42
Q

Why is the substitution of a monodentate ligand with a multidentate ligand less easy to reverse compared to the substitution of two monodentate ligands?

A

The multidentate ligand forms a stronger bond with the central metal ion compared to the monodentate ligand meaning it is harder to reverse the reaction as the complexes are more stable.

43
Q

Why is there hardly any enthalpy change when a ligand exchange occurs?

A

The same number of bonds are broken and made and they have similar bond enthalpies.

44
Q

Why is there an entropy change when a monodentate ligand is exchanged with a multidentate ligand?

A

There are more particles meaning the entropy increases and that makes the complex more stable as reversing the reaction would lead to a decrease in entropy.

45
Q

What are the varying oxidation states of vanadium?

A
46
Q

How is vanadium reduced?

A

Adding it to zinc in an acidic solution.

47
Q

What is a redox potential?

A

How easily something is reduced.

48
Q

What does a very positive redox potential tell us about the stability of an ion?

A

The more positive it is the more likely the ion will be reduced making the ion less stable.

49
Q

How does a change in ligand affect redox potential?

A

If the ligands binding to the central metal ion makes the ion more stable then the redox potential decreases.

50
Q

How does a change in pH affect redox potential?

A

Some ions need H+ ions to be present so they can be reduced so a low pH makes their redox potential more positive. Some ions need OH- ions to be present so they can be reduced so a high pH makes their redox potential more positive.

51
Q

How does Tollen’s Reagent work [Ag(NH3)2]+?

A

The aldehyde is oxidised into a carboxylic acid and the silver ions are reduced into silver atoms which form a silver mirror.

52
Q

What is the equation for the titration of Fe 2+ with MnO4 -?

A
53
Q

What is the equation for the titration of C2O4
2– with MnO4 -.

A
54
Q

Describe a tiration of MnO4- using Fe 2+

A
  1. The reducing agent gets put into the conical flask.
  2. The oxidising agent gets put in the burette.
55
Q

Why are transition metals good catalysts?

A

They can change their oxidation states by losing or gaining electrons. This means that they can transfer electrons to other species to speed up reactions.

56
Q

What is a heterogenous catalyst?

A

The catalyst is in a different phase from the reactants.

57
Q

How does a heterogenous catalyst work?

A

The reactants are adsorbed onto the surface of the catalyst. This causes the bonds in the reactants to weaken and they break. The products then deadsorb from the surface of the catalyst.

58
Q

What is the purpose of a support medium?

A

It increases the surface area of the catalyst and that increases the rate of reaction.

59
Q

What is catalytic poisoning?

A

When impurities are absorbed into the surface of the catalyst preventing the reactants from being adsorbed.

60
Q

How does catalytic poisoning decrease the rate of reaction?

A

It decreases the surface area available for the reactants to be adsorbed.

61
Q

How does catalytic poisoning increase the cost of a chemical process?

A
  1. The catalyst may need to be replaced and that costs money.
  2. Since the rate of reaction decreases less product can be made over a set amount of time and energy.
62
Q

What is a homogenous catalyst?

A

The catalyst is in the same phase as the reactants.

63
Q

How does a homogenous catalyst work?

A

The catalyst reacts with the reactants to form an intermediate species. This then reacts to form the products and reform the catalyst.

64
Q

Write down the equations for Fe2+ catalysing the reaction between S2O8
2– and I–?

A
65
Q

Why is the reaction between S2O8 2– and I– slow without a catalyst?

A

The activation energy is very high as the negative ions repel each other. The iron ions can react with S2O8 2– as they aren’t repelled.

66
Q

How can we test that this reaction has taken place?

A

If we add starch to the solution when iodine is produced the solution will turn blue-black.

67
Q

Write down the equations for Mn2+ autocatalysing the reaction between MnO4– and C2O4
2–?

A
68
Q

Why is the reaction between MnO4– and C2O4 2– slow without a catalyst?

A

The activation energy is very high as the negative ions repel each other. The Mn2+ will not be repelled by the maganate ions.

69
Q

Why is this considered an autocatalysis reaction?

A

Mn 2+ is a product of the reaction and it acts as a catalyst for this reaction. This means that as the reaction goes on the concentration of Mn 2+ ions will increase and that will increase the rate of reaction.

70
Q

Draw and label the concentration of reactants-time graph for this reaction

A