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Chemistry Alevel OCR YR 13 > Transition elements > Flashcards

Transition elements Flashcards

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1
Q

Describe d-block elements

A

-found in the middle of the periodic table
-some elements are transition metals

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2
Q

what is a transition element?

A

d-block element that can form at least one stable ion with a partially filled (incomplete) d-subshell

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3
Q

d-subshell can hold up to how many electrons?

A

10

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4
Q

How does chromium and copper behave differently in electron configuration compared to other transition elements in period 4?

A

An electron from the 4s orbital moves into the 3d orbital to create a more stable half full (Cr) or full 3d sub-shell respectively (Cu)

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4
Q

Why is scandium not a transition element?

A

-scandium forms ion Sc3+
-Sc3+ has an empty d-subshell. As it is not partially filled, it is not a transition element

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5
Q

Why is zinc not a transition element?

A

-Zinc forms ion Zn2+
-Zn2+ has a full d-subshell. As it is not partially filled, it is not a transition element.

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6
Q

How do transition metals lose electrons in a specific way to form ions?

A

lose from 4s first then 3d

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7
Q

What are the properties of transition metals?

A

-variable oxidation states
-form coloured ions in solution
-good catalysts

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8
Q

Why do transition metals have variable oxidation states?

A

because the electrons sit in the 4s and 3d energy levels which are very close. As a result, electrons are gained and lost using a similar amount of energy when they form ions

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9
Q

V 2+ colour?

A

violet

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10
Q

V 3+ colour?

A

green

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11
Q

VO 2+ colour?

A

blue

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12
Q

Cr 3+ colour?

A

green

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13
Q

Cr2O7 2- colour?

A

orange

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14
Q

Mn2+ colour?

A

pale pink

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15
Q

MnO4 2- colour?

A

green

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16
Q

MnO4- colour?

A

purple

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17
Q

Fe2+ colour?

A

pale green

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18
Q

Fe3+ colour?

A

yellow

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19
Q

Co2+ colour?

A

pink

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20
Q

Ni2+ colour?

A

green

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21
Q

Cu2+ colour?

A

blue

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22
Q

Ti2+ colour?

A

violet

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23
Q

Ti3+ colour?

A

purple

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24
Q

Why are transition metals good catalysts?

A

-as they have variable oxidation states they are good catalysts by receiving and losing some electrons in the d-orbitals to speed up reactions
-transition metals have surfaces that allow substances to adsorb which lowers activation energy. Product can be made faster and temperature can be lowered for a reaction which saves energy money and better for environment

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25
Q

What are the risks when using transition metals as catalysts?

A

-copper long term exposure can cause liver damage
-long term manganese exposure can cause psychiatric issues and physical tremors

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26
Q

How does MnO2 (transition metal) act as a catalyst?

A

MnO4 catalyses hydrogen peroxide decomposition.
2 H2O2 -> 2 H2O + O2

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27
Q

How does Fe acts as a catalyst?

A

Fe catalyses the haber process making ammonia.
3 H2 + N2 -> 2NH3

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28
Q

How does CuSO4 act as a catalyst?

A

CuSO4 catalyses zinc + acid reactions.
Zn + H2SO4 -> ZnSO4 + H2

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29
Q

What is the formula for a complex ion?

A

[M(H2O)6] n+ which can be simplified to M n+

30
Q

What is a complex ion?

A

consists of a central metal ion bonded to ligands by coordinate bonds

31
Q

Coordination number definition?

A

number of coordinate bonds attached to a central metal ion

32
Q

Ligand definition?

A

molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond or dative covalent bond

33
Q

What change occurs when OH- or NH3 is added to [Cu(H2O)6]2+?

A

[Cu(H2O)6]2+(aq) blue -> Cu(OH)2(H2O)4(s) pale blue precipitate
-there is no change to the precipitate in excess NaOH
-When excess NH3 is added to the precipitate, [Cu(NH3)4(H2O)2]2+(aq) is formed (dark blue solution), part ligand substitution

34
Q

What change occurs when OH- or NH3 is added to [Fe(H2O)6]2+?

A

[Fe(H2O)6]2+(aq) pale green -> Fe(OH)2(H2O)4(s) dirty green precipitate
-there is no change to the precipitate in excess NaOH
-there is no change to the precipitate in excess NH3

35
Q

What change occurs when OH- or NH3 is added to [Fe(H2O)6]3+?

A

[Fe(H2O)6]3+(aq) yellow -> Fe(OH)3(H2O)3(s) orange precipitate
-there is no change to the precipitate in excess NaOH and in excess NH3

36
Q

What change occurs when OH- or NH3 is added to [Mn(H2O)6]2+?

A

[Mn(H2O)6]2+(aq) pale pink -> Mn(OH)2(H2O)4(s) pink precipitate
-there is no change to the precipitate in excess NaOH and in excess NH3

37
Q

What change occurs when OH- or NH3 is added to [Cr(H2O)6]3+(aq)?

A

[Cr(H2O)6]3+(aq) green -> Cr(OH)3(H2O)3(s) green-grey precipitate
-When excess OH- is added to the precipitate, Cr(OH)6 3-(aq) a dark green solution is formed
-When excess NH3(aq) is added to the precipitate, Cr(NH3)6 3+(aq) purple solution

38
Q

Describe complex ion solution equations

A

reactants: +OH- OR +NH3 (2 moles if ion has 2+ charge, 3 moles if ion has 3+ charge)
products: H2O (2 moles if ion has 2+ charge, 3 moles if ion has 3+ charge)

39
Q

What are monodentate (unidentate) ligands? provide examples

A

ligands which only have one pair electrons . E.g H2O, NH3, CN-, Cl-

40
Q

What are bidentate ligands? provide examples

A

ligands which have 2 lone pairs of electrons. E.g ethanedioate, ethane-1,2-diamine

41
Q

What are multidentate ligands?

A

ligands which have more than one coordinate bond. E.g EDTA 4-, it can form 6 coordinate with the central metal ion

42
Q

How is the shape of a complex ion determined?

A

shape is dependent on the size of the ligands and the coordination number

43
Q

Which ligands are small, meaning you can fit 6 of them around the central metal ion?

A

H2O, NH3 and CN-

44
Q

Which ligand can you fit 4 around the central metal ion?

A

Cl-

45
Q

Which ligand can you fit 3 around the central metal ion?

A

ethanedioate and ethane-1,2-diamine

46
Q

Complexes with coordination number of 6 forms what shape?

A

octahedral shape, all bond angles are 90 degrees

47
Q

complexes with a coordination number of 4 form what shape? provide a specific example

A

forms tetrahedral and square planar shapes.
-bond angles in a tetrahedral complex are 109.5 degrees
-bond angles in a square planar complex are 90 degrees
-anti-cancer drug, cis-platin is a square planar complex

48
Q

How do you calculate the overall charge/oxidation state of a complex ion?

A

oxidation state of metal - total oxidation state of ligands

49
Q

complex ions which are optical isomers are?

A

mirror images e.g octahedral complexes with 3 bidentate ligands

50
Q

Describe cis-trans isomerism in complex ions, octahedral complexes

A

-octahedral complexes with 4 ligands of the same type and 2 of a different type display cis-trans isomerism
-if the 2 different ligands are opposite each other, you have a trans isomer
-if the 2 different ligands are adjacent each other, you have a cis isomer

51
Q

Describe cis-trans isomerism in square planar complex ions

A

-square planar complexes with 2 ligands of the same type and two ligands of a different type display cis-trans isomerism
-If the two different ligands are opposite each other, you have a trans isomer
-If the two different ligands are adjacent each other, you have a cis isomer

52
Q

Describe cis-platin

A

-anti-cancer drug which is a square planar complex with a platinum metal ion, 2 ammonia ligands and two chloride ion ligands.
-chloride ions in complex and easy to displace therefore bonds with nitrogen atoms on DNA of cancer cell can form. This attachment prevent cell division
-however cis-platin can prevent cell division of heathy cells, suppressing the immune system

53
Q

What occurs when a complex ion reacts with a ligand of similar size? Use example of [Co(H2O)6]2+ and NH3

A

substitution reaction occurs and shape doesn’t change (octahedral)
[Co(H2O)6]2+(aq) pink + 6 NH3(aq) -> [Co(NH3)6]2+(aq) STRAW COLOUR + 6H2O(l) full substitution of all ligands has occurred

54
Q

What occurs when a complex ion reacts with a ligand of a different size?

A

there is a change in shape and coordination number

55
Q

What are the changes in colour and shape when [Co(H2O)6]2+(aq) reacts with Cl-(aq)(larger ligand)?

A

[Co(H2O)6]2+(aq) PINK AND OCTAHEDRAL + 4Cl-(aq) -> [CoCl4]2-(aq) BLUE AND TETRAHEDRAL + 6 H2O(l)

56
Q

What are the changes in colour and shape when [Cu(H2O)6]2+(aq) reacts with Cl-(aq)(larger ligand)?

A

[Cu(H2O)6]2+(aq) BLUE AND OCTAHEDRAL + 4 Cl-(aq) -> [CuCl4]2-(aq) YELLOW AND TETRAHEDRAL + 6 H2O(l)

57
Q

What are the changes in colour and shape when [Fe(H2O)6]3+(aq) reacts with Cl-(aq)(larger ligand)?

A

[Fe(H2O)6]3+(aq) YELLOW AND OCTAHEDRAL + 4Cl-(aq) -> [FeCl4]-(aq) YELLOW AND TETRAHEDRAL + 6 H2O(l)

58
Q

describe NH3

A

NH3 IS ONLY USED AS A BASE. IT ACTS AS A LIGAND IN EXCESS

59
Q

three bidentate ligands give what kind of isomerism?

A

optical isomerism (2 mirror images)

60
Q

2 bidentate ligands + 2 monodentate ligands give what kind of isomerism?

A

optical isomerism (2 mirror images) and geometrical isomerism

61
Q

how is ammonia solution made?

A

NH3(g) + H2O(l) -> NH4OH(aq)
NH4+(aq), OH-(aq)

62
Q

the colour of complex ions depends on what?

A

the size of the energy change which is affected by change of oxidation state, co-ordination number and change of ligand

63
Q

Describe the structure of haemoglobin?

A

-haem is a multidentate ligand that is found in the molecule haemoglobin
-octahedral structure
-one of the co-ordinate bonds come from a protein called globin
-the final coordinate bond comes from either an oxygen or water molecule

64
Q

How does haemoglobin work?

A

-oxygen substitutes the water ligand to form oxyhemoglobin
-In a place where oxygen is needed, oxyhemoglobin gives up oxygen and water takes the place

65
Q

Explain how carbon monoxide affects haemoglobin?

A

-the water ligand is replaced with carbon monoxide
-carbon monoxide bonds strongly so its not readily replaced by oxygen or water. This leads to oxygen starvation

66
Q

how are metal-aqua complexes formed?

A

when we add transition metal compound to water

67
Q

How can we identify transition metals?

A

by adding sodium hydroxide solution and observing the colour of the precipitate formed

68
Q

what colour precipitate does Cu2+ form in NaOH solution?

A

blue precipitate

69
Q

what colour precipitate does Fe2+ form in NaOH solution?

A

green precipitate

70
Q

what colour precipitate does Fe3+ form in NaOH solution?

A

orange precipitate

71
Q

what colour precipitate does Mn2+ form in NaOH solution?

A

pink precipitate

72
Q

what colour precipitate does Cr3+ form in NaOH solution?

A

dirty green precipitate

Chemistry Alevel OCR YR 13 (13 decks)

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