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Edexcel A-Level Chemistry > Topic 15 - TRANSITION METALS > Flashcards

Topic 15 - TRANSITION METALS Flashcards

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1
Q

Definition of a transition metal

A

An element that has an incomplete d sub shell in its common ions

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2
Q

Which two period 4 d-block elements are not transition metals and why? (6)

A
  • Transition metals are elements that have an incomplete d sub shell in its common ions
  • Scandium forms Sc3+ ion
  • Electronic configuration of Sc3+: 1s2 2s2 2p6 3s2 3p6
  • In Sc3+, the d orbital is empty
  • Zinc forms Zn2+ ion
  • Electronic configuration of Zn2+: 1s2 2s2 2p6 3s2 3p6 3d10
  • In Zn2+, the d orbital is completely full
  • Therefore Zn and Sc are not transition metals
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3
Q

Electronic configuration of Cr using [Ar]

A

[Ar] 4s1 3d5

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4
Q

Electronic configuration of Cu using [Ar]

A

[Ar] 4s1 3d10

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5
Q

Describe and explain the properties of a transition metal

A
  • High MP/BP
  • High density
  • High tensile strength
  • Large nuclear charge
  • Small atomic radius
  • Strong electrostatic attraction
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6
Q

Why do transition metals have variable oxidation states?

A
  • Energy difference between orbitals
  • So both energy levels can be used for bond formation
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7
Q

Why do transition metals form coloured compounds?

A
  • Gap in energy levels between d orbitals
  • Electrons absorb energy to be promoted to higher energy level
  • We see colour because of the visible light that is not absorbed
  • The colour we see of solids is due to light being reflected
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8
Q

Identify 4 factors that affect the colour of transition metal complexes and explain why they affect colour

A
  • Oxidation state
  • Ligands
  • Co ordination number
  • Shape

All affect size of energy gap between d orbitals and wavelength of light absorbed

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9
Q

What does this equation stand for:
△E = hf = hc/λ

A

△E = gap in energy
h = Planck’s constant (6.63 x 10^-34 J)
f = frequency of light
c = velocity of light
λ = wavelength of light

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10
Q

Definition of a ligand

A

Particle with lone pair of electrons that bonds to metals by a co-ordinate bond

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11
Q

Definition of a complex

A

Metal ion with co-ordinately bonded ligands

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12
Q

Definition of co-ordinate number

A

Number of co-ordinate bonds from ligands to metal ion

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13
Q

What is the shape and angle of a complex with:
- Coordination number: 2
- Contains Ag+ ?

A
  • Planar
  • 180
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14
Q

What is the shape and angle of a complex with:
- Coordination number: 4
- Contains Pt 2+ and Ni 2+ ?

A
  • Square planar
  • 90
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15
Q

What is the shape and angle of a complex with:
- Coordination number: 4
- Contains larger ligands eg Cl- ?

A
  • Tetrahedral
  • 109.5
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16
Q

What is the shape and angle of a complex with:
- Coordination number: 6
- Contains small ligands eg. H2O ?

A
  • Octahedral
  • 90
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17
Q

What is a monodentate ligand and give examples?

A
  • Ligand which has one pair of electrons they can donate to a central metal ion
  • H2O
  • NH3
  • Cl-
  • CN-
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18
Q

What is a bidentate ligand?

A
  • Ligand which can form two dative bonds to the complex ion as it contains two lone pairs of electrons
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19
Q

What is a polydentate ligand and give examples?

A
  • Ligand with more than two atoms with lone pairs of electrons and can form more than two dative bonds to the complex ions
  • EDTA+
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20
Q

How can we identify cisplatin complexes from a diagram?

A

Similar ligands are next to each other

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21
Q

How can we identify transplatin complexes?

A

Similar ligands are opposite each other

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22
Q

What is a ligand substitution?

A

A reaction where one ligand is replaced by another ligand

23
Q

What is the colour of [Cu(H2O)6]2+

A

Blue

24
Q

What is the colour of [Fe(H2O)6]2+

A

Green

25
Q

What is the colour of [Co(H2O)6]2+

A

Pink

26
Q

What is the colour of [Fe(H2O)6]2+

A

Yellow

27
Q

What is the colour of [Cr(H2O)6]3+

A

Green

28
Q

What happens when excess OH- is added to group 2 metals?

A

White ppt forms

29
Q

What is the colour of chromium (III) with some OH-?

A

Green ppt

30
Q

What is the colour of chromium (III) with excess OH-?

A

Green ppt redissolves to dark green

31
Q

What is the colour of iron (III) in OH-?

A

Green ppt which oxidises on standing

32
Q

What is the colour of iron (III) in OH-?

A

Red/brown ppt

33
Q

What is the colour of cobalt (II) in OH-?

A

Blue ppt which turns pink on standing

34
Q

What is the colour of copper (II) in OH-?

A

Blue ppt

35
Q

What is the colour of chromium (III) with some NH3?

A

Green ppt

36
Q

What is the colour of chromium (III) in excess NH3?

A

Green ppt redissolves to form purple ppt

37
Q

What is the colour of iron (II) in NH3?

A

Green ppt which oxidises on standing

38
Q

What is the colour of iron (III) in NH3?

A

Red/brown ppt

39
Q

What is the colour of cobalt (II) in some NH3?

A

Pink solution to blue ppt

40
Q

What is the colour of cobalt (II) in excess NH3?

A

Redissolves to form brown solution that darkens on standing

41
Q

What is the colour of copper (II) in NH3?

A

Ppt redissolves forming dark blue solution

42
Q

What is the colour of Cr2O7 2-?

A

Orange

43
Q

What is the colour of Cr 3+?

A

Green

44
Q

What is the colour of Cr 2+?

A

Pale blue

45
Q

What is the colour of V 2+?

A

Violet

46
Q

What is the colour of V 3+?

A

Green

47
Q

What is the colour of (VO) 2+?

A

Blue

48
Q

What is the colour of (VO2) +?

A

Yellow

49
Q

What happens to the entropy and therefore △G if a ligand is replaced by another which forms more co ordinate bonds?

A
  • Significant increase in entropy
  • And △H is negligible
  • Therefore △G is very negative and reaction is feasible
50
Q

What is the chelate effect?

A

When:
- Ligands are replaced with by another that forms more coordinate bonds
- Reaction is feasible

51
Q

What does a large Kstab mean?

A

Complex formed is very stable

52
Q

What does a small Kstab mean?

A

Complex formed is not very stable

53
Q

Which complexes tend to have a larger Kstab?

A

Complexes containing:
- Bidentate ligands
- Polydentate ligands

Edexcel A-Level Chemistry (16 decks)

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