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Chemistry Module 5 > Transition Metals > Flashcards

Transition Metals Flashcards

1
Q

What is a transition metal?

A

A d-block element that has an ion with an incomplete d-subshell

NOT ALL D-BLOCK ELEMENTS ARE TRANSITION METALS

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2
Q

How do transition metals form positive ions?

A

It loses its valence electrons first (4s-electrons are removed before any d-electrons)

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3
Q

Why is zinc not a transition element?

A

Zinc has a complete d-subshell, therefore Zn does not form at least one ion with an incomplete d-subshell, therefore zinc is not a transition metal

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4
Q

What are the properties of transition metals?

A
  • variable oxidation states
  • formation of coloured compounds and ions
  • catalytic behaviour
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5
Q

Why do transition metals have variable oxidation states?

A

Electrons in the d-subshells are close together in energy, it is almost as easy to to remove several outer electrons as it is to remove only one

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6
Q

Why do transition elements form coloured compounds and ions?

A

Aqueous solutions of transition element ions and their oxyanions are coloured

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7
Q

Why do transition elements display catalytic behaviour?

A
  • they can have diifferent oxidation states so ions can gain or lose electrons very easily
  • empty d-orbitals can accept electrons from other molecules/ions at the transition element surface - intermediate space can be made

Both homogeneous and heterogeneous

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8
Q

Why do transition metals form complex ions when a salt or compound of the metal is dissolved in water?

A

The metal ion does not exist in isolation, so it develops interactions with the molecules that are present in solution

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9
Q

What is a complex?

A

A central metal ion bonded by molecules or negatively charged ions called ligands

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10
Q

What is a ligand?

A

A monodentate ligand is a molecule or ion, which donates a lone pair of electrons to the central metal ion by coordinate bonding (dative covalent bond)

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11
Q

What is the coordination number?

A

The number of coordinate bonds in the complex (not necessarily the number of ligands)

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12
Q

What are bidentate ligands?

A

Some ligands can donate two pairs of electrons to the central metal ion to make two coordinate bonds

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13
Q

What are common bidentate ligands?

A

Ethandioate ion (C2O4 2-)

1,2-diaminoethane (H2NCH2CH2NH2)

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14
Q

What are the three ligand shapes?

A
  • octahedral
  • tetrahedral
  • square planar
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15
Q

What is an octahedral complex ion?

A

Bond angles: 90 and 180 degrees

Coordination number: 6

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16
Q

What is a tetrahedral complex ion?

A

Bond angle: 109.5 degrees

Coordination number: 4

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17
Q

What is a square planar complex ion?

A

Bond angle: 90 degrees

Coordination number: 4

Assume 4 coordinate complexes are tetrahedral unless told otherwise

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18
Q

What is cis platin?

A
  • an anti cancer drug that binds to DNA, preventing cell division
  • [PlCl2(NH3)2]2
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19
Q

What are stereoisomers?

A

The same molecular and structure formula , but different spatial arrangements of their atoms

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20
Q

When does cis-trans isomerism occur in complex ions?

A
  • square planar or octahedral
  • needs to have two MONODENTATE ligands present for square planar
  • two monodentate or two bidentate ligands for octahedral
  • cis bonds have 90 degrees angles, whereas trans bonds have 180 degree angles
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21
Q

What is optical isomerism in complex ions?

A
  • octahedral complexes with two or more bidentate ligands show optical isomerism
  • gives two possible mirror images which are non-superimposable
  • central ion is not chiral
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22
Q

What are precipitation reactions with sodium hydroxide in transition metals?

A

Transition metals react with the hydroxide ions in aqueous solution, creating a precipitate

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23
Q

What is a precipitate?

A

The insoluble product of a reaction between two aqueous solutions

24
Q

What are ligand substitution reactions?

A

Electron pair donors can be replaced by other ligands to form more stable complexes

25
What happens when Fe (III) and thiocyanate ions (SCN-) are added together?
The yellow Fe (III) solution will change colour to blood red [Fe(H2O)6]3+ (aq) + SCN- (aq) ————>[Fe(H2O)5(SCN)]2+(aq) + H2O(l)
26
Explain the observation when an excess of concentrated HCl is added to aqueous CuSO4
- HCl is a source of chloride ligands - concentration of Cl- so equilibrium shifts more to the RHS - solution becomes more yellow as more [CuCl4]2- forms
27
Why is ligand substitution important in the transport of oxygen by haemoglobin?
- haem contains an Fe(II) iOS, which forms four coordinate bonds to the four nitrogen atoms in the haem ligan and to one nitrogen atom in the globin - oxygen can also form a bond with the Fe 2+, allowing it to be transported through the body
28
With reference to haemoglobin, explain why carbon monoxide is importan
- carbon monoxide acts as a ligand its Fe 2+ ion, replacing oxygen in a ligand substitution reaction - carbon monoxide forms a stronger bond so CO is toxic by inhaliation
29
What colour is Cu 2+ in solution?
Blue solution [Cu(H2O)6] 2+ (aq)
30
What colour is Mn 2+ in solution?
Very pale pink solution [Mn(H2O)6] 2+ (aq)
31
What colour is Fe 2+ in solution?
Pale green solution [Fe(H2O)6] 2+ (aq)
32
What colour is Fe 3+ in solution?
Pale yellow solution [Fe(H2O)6] 3+ (aq)
33
What colour is Cr 3+ in solution?
Violet solution = [Cr(H2O)6] 3+ (aq) Green solution = [Cr(H2O)5SO4] + (aq)
34
What colour is Cu 2+ when reacted with OH-?
Blue precipitate Cu(OH)2 (s)
35
What colour is Mn 2+ when reacted with OH-?
Light brown precipitate Mn(OH)2 (s)
36
37
What colour is Fe 2+ when reacted with OH-?
Green precipitate Fe(OH)2 (s)
38
What colour is Fe 3+ when reacted with OH-?
Orange-brown precipitate Fe(OH)3 (s)
39
What colour is Cr 3+ when reacted with OH-?
Grey-green precipitate Cr(OH)3 (s)
40
What colour does Mn(OH)2 (s) when left standing in O2?
It darkens to a darker brown precipitate Mn(OH)3 (s)
41
What colour does Fe(OH)2 (s) turn when left standing in O2?
It darkens from a green precipitate to an orange-brown precipitate Fe(OH)3 (s)
42
What colour does Cu 2+, Mn 2+, Fe 2+, Fe 3+, Cr 3+ form when reacted with excess OH-?
Cu 2+ = insoluble Mn 2+ = insoluble Fe 2+ = insoluble Fe 3+ = insoluble Cr 3+ = dark green solution (grey-green ppt re-dissolves)
43
What colour is Cu 2+ when reacted with NH3?
Blue precipitate Cu(OH)2 (s)
44
What colour is Mn 2+ when reacted with NH3?
Light brown precipitate Mn(OH)2 (s)
45
What colour is Fe 2+ when reacted with NH3?
Green precipitate Fe(OH)2 (s)
46
What colour is Fe 3+ when reacted with NH3?
Orange-brown precipitate Fe(OH)3 (s)
47
What colour is Cr 3+ when reacted with NH3?
Grey-green precipitate Cr(OH)3 (s)
48
What colour is Cu 2+ when reacted with excess ammonia?
Dark blue solution [Cu(NH3)4(H2O)2] 2+ (aq)
49
What colour are Mn 2+, Fe 2+, Fe 3+ when reacted with excess ammonia?
All insoluble so don’t change colour
50
What colour is Cr 3+ when reacted with excess ammonia?
Purple solution [Cr(NH3)6] 3+ (aq)
51
What colour is Cu 2+ when reacted with concentrated HCl?
Yellow solution [CuCl4] 2- (aq)
52
What colour is MnO4 -?
Deep purple solution
53
What colour is Cr2O7 2-?
Orange solution
54
What colour is CrO4 2-?
Yellow solution
55
What colour is CuI (s)?
White precipitate
56
What colour is I2 (aq)?
Brown solution (blue-black with starch)

Chemistry Module 5 (3 decks)

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