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Chemistry > 3.2.5 - Transition Metals > Flashcards

3.2.5 - Transition Metals Flashcards

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1
Q

Transition metals

A

Elements in the d-block of the periodic table with a partially filled d-orbital. They lose electrons to form positive ions with the s-orbital electrons being removed first

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2
Q

Physical properties of transition metals

A

Similar physical properties, atomic radius, high densities and high melting and boiling points

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3
Q

Chemical properties of transition metals

A

Form complexes, form coloured ions, variable oxidation states, good catalysts

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4
Q

Complexes

A

form from transition metals, consisting of a central metal ion or atom surrounded by ligands

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5
Q

Ligands

A

Molecules or ions with a lone electron pair that is able to form a coordinate bond to the central metal ions by donating this electron pair.

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6
Q

Common ligands

A

Cl-
H2O
NH3

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7
Q

Coordination number

A

Equal to the number of coordinate bonds formed around the central metal ion

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8
Q

Coordination number of silver complexes

A

2

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9
Q

Common coordination number of platinum complexes

A

4

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10
Q

Exchange between ligands NH3 and H2O

A

They can be exchanged without a change in coordination number via a ligand substitution reaction

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11
Q

Equation for ligand substitution reaction between NH3 and H2O ligands

A

[Co(H2O)6]2+ + 6NH3 –> [Co(NH3)6]2+ + 6H2O

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12
Q

Exchange between copper complexes and NH3 in excess

A

The substitution is incomplete and the complex formed has a combination of water and ammonia ligands

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13
Q

Equation for reaction between [Cu(H2O)6]2+ and NH3

A

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

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14
Q

colour of [Cu(H2O)2(NH3)4]2+

A

forms as a deep blue solution

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15
Q

Exchange between copper complexes and Cl-

A

Cl- ligand is much larger than NH3 and H2O ligands meaning substitution with this ligand results in a change in coordination number for that complex

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16
Q

Equation for reaction between [Cu(H2O)6]2+ and Cl-

A

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

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17
Q

Complexes with just Cl- ligands always have…

A

a coordination number of 4, producing a tetrahedral shaped complex

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18
Q

Bidentate ligands

A

Able to form two coordinate bonds to the central metal ion as they have two lone electron pairs

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19
Q

Common bidentate ligands

A

Ethanedioate ions, ethane-1,2-diamine

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20
Q

Ethanedioate ions

A

a lone pair electron on two of the oxygen atoms

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21
Q

Ethane-1,2-diamine

A

a lone electron pair on each of the nitrogen atoms

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22
Q

Multidentate ligands

A

Able to form up to six coordinate bonds to the central metal ion as they have multiple lone electron pairs

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23
Q

Most common multidentate ligand

A

EDTA (ethylenediaminetetraacetic acid)

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24
Q

Equation for reaction between iron compound and EDTA

A

[Fe(H2O)6]3+ + EDTA4- –> [FeEDTA]-1 + 6H2O

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25
Q

Another common multidentate ligand is…

A

Haem that consists of six coordinate bonds around a central Fe2+ ion and its shape & structure allow it to transport oxygen

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26
Q

Carbon monoxide

A

toxic to humans as it replaces the oxygen in the haem complex thus preventing it from being transported around the body

27
Q

The chelate effect

A

more moles on the right is achieved by substituting unidentate ligands with bidentate or multidentate ligands

28
Q

Positive entropy change

A

favourable as it means a more stable complex is being formed, it is favourable to have more moles on the right than the left

29
Q

Enthalpy change

A

very small as bonds being formed are very similar to the bonds that were broken

30
Q

Octahedral complexes

A

transition metal complexes with H2O and NH3 ligands commonly for octahedral complexes, bond angle 90°

31
Q

Cis-trans isomerism

A

shown by octahedral complexes with different types of unidentate ligands where ligands of the same type can be opposite or next to each other

32
Q

trans isomer

A

has two of the same ligands opposite each other

33
Q

cis isomer

A

has two of the same ligands next to each other

34
Q

optical isomerism

A

shown by octahedral complexes with bidentate ligands where the two isomers are mirror images of each other

35
Q

tetrahedral complexes

A

Form when complexes for with larger ligands e.g. Cl-, bond angle 109.5°. Can show optical isomerism

36
Q

Square planar complexes

A

form in Platinum and Nickel complexes, 4 coordinate bonds, bond angle 90°

37
Q

Linear complexes

A

form in silver complexes, 2 coordinate bonds, bond angle 180°

38
Q

Cisplatin

A

cis isomer of square planar complex of platinum

39
Q

Uses of cisplatin

A

cancer therapy drug

40
Q

Observing colour of compounds

A

White light shines on a substance some wavelengths are absorbed but remaining are reflected & transmitted to the eye. These reflected wavelengths correspond to a specific colour which is observed

41
Q

Electrons in the d-orbital…

A

exist in a series of energy states, when given energy they move from the ground state to the excited state. ∆E corresponds to a wavelength and frequency of light

42
Q

Colorimetry

A

An analytical technique that uses the absorption of visible light to determine the concentration of coloured ions by measuring absorbance

43
Q

Calibration graph

A

Produced by measuring solutions of known concentrations which can then be used to calibrate the colorimeter on a graph of relative absorbance against concentration

44
Q

Oxidation state of Vanadium in VO_2+

A

+5

45
Q

Ion colour of VO_2+

A

yellow

46
Q

Oxidation state of Vanadium in VO^2+

A

+4

47
Q

Ion colour of VO^2+

A

blue

48
Q

Oxidation state of V3+

A

+3

49
Q

Ion colour of V3+

A

green

50
Q

Oxidation state of V2+

A

+2

51
Q

Ion colour of V2+

A

violet

52
Q

Conditions for ions to be reduced

A

acidic

53
Q

Equation of reduction of VO_2+

A

2VO_2+ + 2e- + 4H+ –> 2VO^2+ + 2H2O

54
Q

Conditions for ions to be oxidised

A

alkaline as they react with water to produce OH- ions

55
Q

Equation for oxidation of VO^2+

A

VO^2+ + H2O –> VO_2+ + 2H+ + e-

56
Q

[Ag(NH3)2]+ (Tollens Reagent) is reduced by…

A

aldehydes to form silver atoms

57
Q

Equation for reduction of Tollens Reagent

A

RCHO + 2[Ag(NH3)2]+ + 3OH- –> RCOO- + 2Ag + 4NH3 + 2H2O

58
Q

Heterogeneous catalyst

A

catalysts that are in a different phase to the species in the reaction

59
Q

Variable oxidation states make transition metals…

A

Good catalysts, electrons are transferred to produce a reactive intermediate and speed up the reaction rate

60
Q

Homogeneous catalyst

A

catalysts are in the same phase to the species in the reaction

61
Q

Adsorption

A

A solid catalyst works adsorbed molecule onto an active site on the surface of the catalyst. These active sites increase the proximity of molecules and weaken covalent bonds in molecules

62
Q

Catalyst poisoning

A

Heterogeneous catalysts can be poisoned by impurities which block active sites and prevent adsorption

63
Q

Homogeneous catalysts work by…

A

combining with reactants to produce a reactive intermediate which changes reaction path, activation energy is lower

Chemistry (32 decks)

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