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A2 Chemistry > transition metals > Flashcards

transition metals Flashcards

1
Q

what is a transition element?

A

an element which forms a stable ion which has a partially filled d sub shell

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2
Q

what is a d block element?

A

an element which has its electrons in its d sub shell

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3
Q

which d block elements aren’t transition metals and why?

A

scandium - has no electrons in its d sub shell when it forms an ion
zinc - has a full d sub shell when it forms an ion

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4
Q

out of the 4s and 3d sub shell, which one fills up first?

A

4s

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5
Q

what is the electron configuration of a chromium ion?

A

[Ar] 4s1 3p5

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6
Q

what is the electron configuration of copper?

A

[Ar} 4s1 3d10

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7
Q

give some of the properties of transition elements?

A

forms coloured ions
acts as a catalyst
has variable oxidation states
can form complexes

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8
Q

what’s a complex?

A

a molecule with a transition metal ion in the centre with ligands coordinately bonded to them

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9
Q

what is a ligand?

A

an atom or a molecule that donates a pair of electrons to a central metal ion to form a coordinate bond

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10
Q

what is the coordination number?

A

the number of coordinate bonds formed to a central metal ion

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11
Q

what is a monodentate ligand?

A

atoms or molecules which only form one coordinate bond to the complex ion

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12
Q

give some examples of monodentate ligands

A

Cl-, NH3, H2O, OH- and CN-

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13
Q

what are bidentate ligands?

A

molecules which have two atoms which each have a lone pair of electrons which can each form a coordinate bond to a central metal ion

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14
Q

give an example of a bidentate ligand

A

ethane-1,2-diamine - H2NCH2CH2NH2

C2O4^2-

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15
Q

what are multidentate ligands?

A

ligands which can form more than one coordinate bond to a central metal ion because they have multiple atoms with lone pairs available to form coordinate bonds

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16
Q

give an example of a multidentate ligand

A

EDTA

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17
Q

how many coordinate bonds does EDTA form?

A

6

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18
Q

what is a ligand substitution reaction?

A

a reaction where one ligand which is coordinately bonded to a central metal ion is replaced by another ligand

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19
Q

when does a ligand substitution reaction with no change in coordination number occur?

A

when small and uncharged ligands are used

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20
Q

what is haem?

A

an iron(II) complex with a multidentate ligand

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21
Q

how does haemoglobin carry oxygen?

A

Oxygen forms a co-ordinate bond to Fe(II) in haemoglobin, enabling oxygen to be transported in the blood.

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22
Q

why is carbon monoxide toxic?

A

replaces oxygen, co-ordinately bonded to Fe(II) in haemoglobin so oxygen can’t be carried

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23
Q

what is the chelate effect?

A

when bidentate and multidentate ligands replace monodentate ligands in a complex

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24
Q

what is the link between coordination number and the enthalpy change?

A

no change in coordination number = no enthalpy change

more coordinate bonds broken than made means an increase in enthalpy

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25
Q

what determines the entropy change of a ligand substitution reaction?

A

the number of reacting particles and the number of product particles

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26
Q

what is the shape of a complex with 6 coordinate bonds joined to it?

A

octahedral

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27
Q

what is the bond angle in octahedral complexes?

A

90

28
Q

which octahedral complexes form E-Z isomers?

A

Those in the form of ML4A2 (all monodentate)

29
Q

which octahedral complexes can form optical isomers?

A

Those formed from bidentate ligands

30
Q

what is the bond angle in tetrahedral complexes?

A

109.5

31
Q

give some examples of tetrahedral complexes

A

[CuCl4}2-
[CoCl4]2-
[FeCl4]-

32
Q

what is cisplatin

A

an ant-cancer drug

33
Q

what kind of isomerism does cisplatin show?

A

E-Z isomerism

34
Q

in what form is cisplatin active?

A

the Z form

35
Q

how does cisplatin work?

A

forms bonds between the bases in DNA so it stops DNA replication in tumour cells and stops tumours from growing

36
Q

what is the bond angle in square planar complexes?

A

90

37
Q

what happens to the d sub shell when a complex is formed?

A

it’s split into two different orbitals at two different energy levels

38
Q

how are transition metal complexes coloured?

A

when they’re hit by light, light is absorbed and promotes electrons from ground state to excited state
some light is absorbed
colour arises when other wavelengths are transmitted

39
Q

what does the colour of a complex depend on?

A

shape of the complex
ligands attached to it
coordination number
metal ions and different charges

40
Q

what formula can you use to calculate energy difference between orbitals?

A

delta E = hv = hc/v

h = Planck constant
c = speed of light
v = frequency Hz
41
Q

give an example of a linear compound

A

[Ag(NH3)2]+

42
Q

what is colorimetry?

A

the measurement of colour intensity using a colorimeter

43
Q

how does a colorimeter work?

A

light shone through a sample and absorbance calculated
filter used to get a specific wavelength of light
absorbance compared against a calibration curve

44
Q

when do you use a spectrophotometer?

A

when the compound is colourless so colorimetry can’t be used as the compound doesnt absorb visible light but does absorb UV light

45
Q

how can vanadium be reduced?

A

by a reducing agent such as zinc in the presence of an acid

46
Q

describe the colour change as vanadium goes from +5 to +2

A

yellow —> blue —> green —> violet

47
Q

what is tollen’s reagent used for?

A

testing for the presence of aldehydes and ketones

48
Q

what is potassium manganate used for?

A

titrations - testing how many moles of acid and alkali there are

49
Q

what is a homogenous catalyst?

A

a catalyst which is in the same physical state as the reactants

50
Q

what is a heterogenous catalyst?

A

a catalyst which is in a different phase to the reactants

51
Q

explain how catalysts work

A

by chemisorption

  • reactants are adsorbed onto the active site on the surface of the catalyst
  • reactant bonds weakened
  • held in a more favourable shape
  • product molecules leave the catalyst’s surface
52
Q

how can catalysts be poisoned?

A

a substrate binds irreversibly to the active site so they have a reduced efficiency

53
Q

what are the implications of catalyst poisoning?

A

have to be replaced which is expensive

54
Q

how can catalyst poisoning be reduced?

A

purify reactants before reacting them

55
Q

what is autocatalysis?

A

when the product in a reaction acts as a catalyst for the reaction

56
Q

why is the reaction of manganate ions and ethanedioate ions slow at first?

A

both negatively charged so they repel each other because of the high activation energy

57
Q

why does the rate of reaction increase as manganate and ethanedioate ions react?

A

because Mn^2+ is formed which catalyses the reaction

58
Q

why can manganese and iron act as catalysts?

A

they have variable oxidation states

59
Q

what is the test for 3+ ions?

A

adding sodium carbonate and seeing if there’s effervescence

60
Q

why are 3+ ions more acidic?

A

higher charge
draw electrons in more (away from H)
H is a better leaving group
complex therefore acts as an acid

61
Q

what colour is potassium mangante in acid?

A

colourless

62
Q

what colour is potasium manganate in alkali?

A

purple

63
Q

name an example of homogenous catalysis?

A

S2O8^2- and I-

64
Q

give an example of autocatalysis?

A

MnO4- and C2O4^2-

65
Q

why is the reaction of MnO4- and C2O4^2- slow at first?

A

ions repel each other
high activation energy
small amount of catalyst at first

A2 Chemistry (17 decks)

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