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OCR Chemistry A Level Module 5 Physical chemistry and transition elements > 5.3.1 Transition metals > Flashcards

5.3.1 Transition metals Flashcards

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1
Q

What are d block elements?

A
  • between Grp 2 and 13, with highest energy electrons in 3d orbitals
  • metallic: high mp and bp, shiny, and conduct electricity and heat
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2
Q

Write out the electronic configurations for copper and chromium?

A

Cr: 1s2 2s2 2p6 3s2 3p6 3d5 4s1

Cu: 1s2 2s2 2p6 3s3 3p6 3d10 4s1

for stability

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3
Q

Whats special about ions forming with d block elements? E.g. give electronic configuration of Fe2+

A
  • they lose 4s e- first before losing 3d

1s2 2s2 2p6 3s2 3d6

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4
Q

Define transition elements

A
  • d block elements that form at least one ion with partially filled d-orbital (scandium and zinc are NOT transition metals)
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5
Q

State and describe the 3 properties of transition metals

A
  1. variable oxidation numbers -> all form +2 in compounds, manganese up to +7
  2. coloured compounds -> colour linked to partially filled d-orbitals of transition metal ion + can vary with diff oxidation states
  3. catalysts

heterogenous
- haber: iron
- hydrogenation: nickel
- hydrogen peroxide decomposition: MnO2
- contact process: V2O5

homogenous
- Fe2+ ions in reaction of iodide ions and S2O8 2-.

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6
Q

Define ligand

A

molecule/ion that donates a pair of electrons to a central metal ion to form a coordinate/ dative covalent bond to form a complex

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7
Q

Define coordination number

A

indicates the no. of bonds attached to the central metal ion

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8
Q

What is monodentate vs bidentate? What are the key examples?

A

mono: donate ONE pair of electrons to central metal ion (water, ammonia, OH-, Cl-)

bi: donate TWO pairs of electrons to central metal ion (C2O4 2-, NH2CH2CH2NH2)

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9
Q

How do you represent complex ions?

A

[Cr(H2O)6] 3+

ion inside square brackets
ligand inside round brackets

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10
Q

What is the shape for coordination numbers:
a) 6
b) 4
c) 2

A

a) octahedral (90 degrees)
b) tetrahedral (109.5 degrees) or square planar (90 degrees) when there are 8 d electrons in the highest energy d sub shell
c) linear (180 degrees)

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11
Q

Which shape complex ions show cis-trans isomerism?

A

Some four (square planar) and six coordinate (octahedral) complex ions with 2 diff monodentate ligands

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12
Q

Which shape complex ions show cis-trans AND optical isomerism?

A

Some six-coordinate complex ions containing monodentate and bidentate ligands

Optical isomerism only in octahedral complexes containing 2 or more bidentate ligands e.g. 3

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13
Q

What is cis platin used for?

A

Used as an anti cancer drug since it forms a complex in a cell which binds to DNA and prevents it from replicating

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14
Q

Describe the cis vs trans isomer for octahedral monodentate and bidentate e.g. using angles

A

Cis: 90 degrees between the same type of ligand (they’re next to each other)
Trans: 180 between the same type of ligand (opposite each other)

Bidentate is the same thing

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15
Q

What is ligand substitution?

A

One ligand in a complex ion is replaced by another ligand

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16
Q

Copper (II) sulfate in water forms which ion?

A

[Cu(H2O)6] 2+

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17
Q

[Cu(H2O)6]2+ colour

A

Pale blue

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18
Q

Write equations for ligand substitutions of [Cu(H2O)6]2+ (e.g with ammonia and with HCl)

What happens when dropwise ammonia is added compared to excess?

A

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

With dropwise ammonia added, Cu(OH2) precipitate forms then dissolves in excess ammonia to form the complex ion

EXCESS CONC HCL:
[Cu(H2O)6]2+ +4CL- <-> [CuCl4]2- + 6H2O (green intermediate due to mixture of solutions)

19
Q

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

A

Dark blue

20
Q

Cu(OH)2 Colour

A

Pale blue

21
Q

[CuCl4]2- colour

A

Yellow

22
Q

Water + [CuCl4]2- forms what?

A

Goes back to blue Colour but more dilute/paler

23
Q

Why does coordination number change when HCl is added?

A

Since chloride ligands are larger so fewer can fit around central ion compared to water molecules in copper(II) sulfate complex ion

24
Q

KCr(SO4)2 . 12H2O in water = [Cr(H2O)6]3+ and which Colour?

A

Violet

25
Q

Cr3+ ions in solution

A

Green

26
Q

What equations if you add excess or drop wise ammonia to [Cr(H2O)6]3+?

A

EXCESS: [Cr(H2O)6]3+ +6NH3 -> [Cr(NH3)6]3+ + 6H2O

DROPWISE
Cr(OH)3 forms first, then dissolves in excess ammonia

27
Q

Cr(OH)3 colour

A

Grey-green

28
Q

Why is haemoglobin important and what does CO do?

A

O2 and CO2 can bind and be transported around the body due to Fe2+ haem groups

CO can also bind to form carboxyhaemoglobin -> ligand substitution occurs where oxygen is replaced, and CO binds much more strongly (irreversibly) = death

29
Q

What is precipitation?

A

Two aq solutions containing ions react together to form an insoluble ionic solid

30
Q

Which ions react with NaOH to make precipitates which are insoluble in excess NaOH?

A

Cu2+, Fe2+, Fe3+, Mn2+

31
Q

Cu2+ ions

A

Blue

32
Q

Fe2+ ions

A

Pale green

33
Q

Mn2+ ions

A

Pale pink

33
Q

Fe3+ ions

A

Yellow

34
Q

Fe(OH)2

A

Green

35
Q

Fe(OH)3 colour

A

This occurs when Fe(OH)2 is exposed to air -> brown at surface

Or just orange-brown

36
Q

Mn(OH)2 colour

A

Light brown (and darkens in air)

37
Q

Which precipitate dissolves in excess NaOH and what is the equation?

A

Cr(OH)3 + 3OH- -> [Cr(OH)6]3-

38
Q

[Cr(OH)6]3- colour

A

Dark green

39
Q

Excess NH3 to Cu2+ and Cr3+ ions description

A

Form precipitates
These dissolve to form aq colored solutions

40
Q

Excess NH3 to Fe2+, Fe3+, and Mn2+ ions description

A

Form precipitates
No dissolving

41
Q

Explain why ethane-1,2-diamine can act as a bidentate ligand

A

(N) can donate 2 electron pairs to the central metal ion, forming 2 coordinate bonds

42
Q

Explain why scandium and zinc are classified as d block elements but are NOT also transition metals (4)

A

Transition element: has an ION with an incomplete d sub-shell

D block since d orbital has highest energy

Sc: 1s2 2s2 2p6 3s2 3p6 3d1 4s2
Zn: 1s2 2s2 2p6 3s2 3p6 3d10 4s2

Sc3+: 1s2 2s2 2p6 3s2 3p6 -> d sub-shell empty
Zn2+: 1s2 2s2 2p6 3s2 3p6 3d10 -> d sub-shell full

OCR Chemistry A Level Module 5 Physical chemistry and transition elements (7 decks)

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