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Chemistry Module 5 > 5.3.1 Transition elements > Flashcards

5.3.1 Transition elements Flashcards

1
Q

why do transition metal elements form certain characteristics

A

due to incomplete d sub-level in ions

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2
Q

characteristics of transition metals

A

formation of coloured ions
variable oxidation states
catalytic activity
complex ion formation

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3
Q

which elements aren’t classed as transition elements

A

zinc

scandium

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4
Q

why is zinc not classed as a transition metal

A

Zn can only form a 2+ ion
in this ion Zn2+ has a complete d orbital and so doesn’t meet the criteria of having an incomplete d orbital in one of its ions

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5
Q

why is scandium not classed as a transition metal

A

Sc can only form 3+ ion, in this ion Sc3+ has an empty d orbital so doesn’t meet the criteria of having an incomplete d orbital in one of its ions

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6
Q

3 typical properties of transition elements

A

existence of more than one oxidation state in its compounds
form coloured ions
behave as catalysts

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7
Q

existence of more than one oxidation state in its compounds

A

e.g. iron normally forms +2 and +3

chromium can form +2 +3 +6

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8
Q

form coloured ions

A

the colours can vary depending on the oxidation state

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9
Q

behaviour as catalysts

A

iron in haber process to make ammonia

manganese dioxide to decompose hydrogen peroxide

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10
Q

complex ion definition

A

central metal ion surrounded by ligands

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11
Q

ligand definition

A

an atom, ion or molecule which donate an electron pair

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12
Q

co-ordinate bonding

A

when shared pair of electrons in the covalent comes from only one of the bonding atoms

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13
Q

co-ordination number

A

number of co-ordinate bonds formed to a central metal ion

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14
Q

what can ligands be

A

unidentate
bidentate
multidentate

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15
Q

unidentate

A

form one co-ordinate bond per ligand

H2O, NH3 and Cl-

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16
Q

bidentate

A

two atoms with lone pairs and can form two co-ordinate bonds per ligand
NH2CH2CH2NH2 and ethanedioate ion C2O4 2-

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17
Q

multidentate

A

can form multiple bonds per ligand

EDTA4- can form 6

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18
Q

EDTA4-

A

6 donor sites (4O and 2N)

forms a 1:1 complex with metal (11) ions

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19
Q

what shape complexes do transition metals form with small ligands

A

octrahedral

with H2O and NH3

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20
Q

what shape complexes do transition metals form with larger ligands

A

tetrahedral

with Cl-

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21
Q

what shape is cisplatin

A

square planar

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22
Q

what shape does Ag+ normally form

A

linear

23
Q

what types of stereoisomerism can complexes show

A

cis-trans and optical

24
Q

cis isomerism

A

normally known as Z isomers

on zee-zame-zide

25
Q

trans isomerism

A

normally known as E isomers

26
Q

complexes with 3 bidentate ligands

A

can form 2 optical isomers

non-superimposable mirror images

27
Q

use of cisplatin

A

anticancer drug

28
Q

how does cisplatin work

A

binds to the DNA of cancer cells and stops cancer cells dividing
causes cell apoptosis

29
Q

reactions with excess NH3

A

ligand substitution
occurs with several transition aqueous ions

[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4(H2O)2]2+ +4H2O

blue to deep blue

30
Q

why is ligand substitution with Cu incomplete?

A

as not all the water molecules are substituted

31
Q

ligand exchange Co and Cr with excess NH3

A

NH3 and H2O are similar in size and are uncharged

so ligand exchange occurs without change of co-ordination number

32
Q

ligand reactions with chloride ions

A

addition of a high conc of chloride ions (from a conc chlorine containing acid) to an aqueous ion leads to a ligand substitution reaction
in Cu and Co changes coordination number from 6 to 4

33
Q

why in reactions with chloride ions can co-ordinate number change

A

because the Cl- ligand is larger and charged compared to H2O and NH3

34
Q

copper reaction with chloride ions

A

[Cu(H2O)6]2+ + 4Cl- -> [CuCl4]2- + 6H2O

blue to yellow/green

35
Q

cobalt reaction with chloride ions

A

[Co(H2O)6]2+ + 4Cl- -> [CoCl4]2- + 6H2O

pink to blue

36
Q

what is formed if solid metal chloride is dissolved in water

A

aqueous [METAL(H2O)6]2+ complex rather than the

chloride [METALCl4]2-

37
Q

biological complexes

A

iron 2 ion in haemoglobin
haem is an iron 2 complex with a multidentate ligand
O2 bonds to Fe2+ ions in the haemoglobin
CO is toxic to humans as it forms a strong coordinate bond with haemoglobin, stronger than with oxygen so prevents the binding

38
Q

what are the ions involved in the precipitation reactions with sodium hydroxide and ammonia

A 
Cu2+
Mn2+
Fe2+
Fe3+
Cr3+
39
Q

basic form of the full equation for ppt reactions with NaOH

A

[metal (H2O)6] ^metal charge + 2OH- -> metal (H2O)6- charge of metal(OH)charge of metal + charge of metal H2O

40
Q

copper ppt reaction with NaOH

A

Cu2+ (aq) + 2OH- -> Cu(OH)2 (s)

blue solution to blue ppt

ppt is insoluble in excess sodium hydroxide

41
Q

manganese ppt reaction with NaOH

A

Mn2+ (aq) + 2OH- (aq) ->Mn(OH)2 (s)

very pale pink solution to pale brown ppt, darkens when in contact with air

ppt is insoluble in excess sodium hydroxide

42
Q

iron(II) ppt reaction with NaOH

A

Fe2+(aq) +2OH- (aq) ->Fe(OH)2 (s)

pale green solution to green ppt

ppt insoluble in excess but in contact with air will turn brown as Fe(II) is oxidised to Fe(III), orange-brown

Fe(OH)2 (s) -> Fe(OH)3 (s)

43
Q

iron (III) ppt reaction with NaOH

A

Fe3+ (aq) + 3OH- (aq) -> Fe(OH)3 (s)

pale yellow to orange-brown

ppt is insoluble in excess sodium hydroxide

44
Q

chromium (III) reaction with NaOH

A

Cr3+ (aq) +3OH- (aq) -> Cr(OH)3 (s)

violet to grey-green ppt

is soluble in excess and will form dark green solution
Cr(OH)3 (s) + 3OH- (aq) -> [Cr(OH)6]3+ (aq)

45
Q

What happens to copper and chromium in excess ammonia

A

Their hydroxide ppts will dissolve

46
Q

Chromium in excess ammonia

A

Cr(OH)3(H2O)3 (s) + 6NH3 (aq) -> [Cr(NH3)6]3+ (aq) +3H2O (l) + 3OH- (aq)

Cr becomes [Cr(NH3)6]3+ purple solution

47
Q

Copper in excess ammonia

A

Cu(OH)2(H2O)4 (s)+ 4NH3 (aq) -> [Cu(NH3)4(H2O)2 (aq) +2H2O (l) + 2OH- (aq)`

Becomes deep blue

48
Q

Which electrons do transition elements lose first

A

Their 4s before the 3D

49
Q

Iron (II) oxidation

A

Easily oxidized to Fe3+ green -> brown, normally use potassium manganate (VII) but oxygen in air also works

MnO4- (aq) + 8H+(aq) + 5Fe2+ (aq) -> Mn2+ (aq) +4H2O (l) + 5Fe3+ (aq)
Purple to colourless

50
Q

Iron (III) reduction

A

Brown to green using potassium iodide
Brown colour of iodine can mask the colour change

2FE3+ (aq) + 2I- (aq) -> I2 (aq) + 2Fe2+ (aq)

51
Q

Reducing chromium

A

Cr3+ (green) and Cr2+ (blue) commonly formed by reduction of Cr2O7 2- (orange) by strong reducing agent zinc in HCl acid solution. Fe2+ is a less strong reducing agent so will only reducing dichromate to Cr3+

Cr2O7 2- + 14H+ + 6Fe2+ -> 2Cr3+ + 7H2O + 6Fe3+
Orange to green

52
Q

Oxidizing chromium

A 
Alkaline chromium (III) can be oxidized using hydrogen peroxide, easier to oxidize a negative ion
Chromium after being in excess NaOH

Cr(OH)6 3- (aq) —-(H2O2)—> CrO4 2- (aq)
Green to yellow
Reduction in this reaction: H2O2 + 2e- -> 2OH-

53
Q

Reduction of Cu2+ to Cu+

A

Potassium iodide
Copper (II) is blue
2Cu2+ (aq) + 4I- (aq) -> I2 (aq) + 2CuI (s)

Brown solution and white ppt

54
Q

Disproportionation of copper(I) ions

A

When reacting with sulfuric acid will disproportionate to Cu2+ and Cu metal

2Cu+ -> Cu + Cu2+

Full equation: Cu2O + H2SO4 -> CuSO4 + Cu + H2O

Chemistry Module 5 (7 decks)

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