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Chemistry > 24) Transition elements > Flashcards

24) Transition elements Flashcards

1
Q

For which two elements does the expected principle of electrons filling singly in orbitals before pairing does not apply?

A

Chromium (3d5 4s1) and Copper (3d10 4s1)

the 1/2 full or fully filled 3d sub-shell to give additional stability

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2
Q

Define transition element

A

a d-block element which forms an ion with an incomplete d-sub-shell
(not Sc -> Sc3+ or Zn -> Zn2+)

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3
Q

Give 3 features of transition elements

A
  • form compounds in which the transition element has different oxidation states
  • form coloured compounds
  • the element and their compounds can act as catalysts e.g. vanadium (V) oxide in the Contact process - production of sulfur dioxide
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4
Q

What is a species containing a transition element in its highest oxidation state often?

A

a strong oxidising agent

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5
Q

Define complex ion

A

a transitional metal ion bonded to ligands by coordinate (dative covalent) bonds

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6
Q

When is a complex ion formed?

A

when 1 or more molecules / anions (ligands) bond to a central metal ion

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7
Q

Define ligand

A

a molecule or ion that can donate a pair of e- to the transitional metal ion

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8
Q

Define coordinate bond

A

a shared pair of e- in which the bonded pair has been provided by one of the bonding atoms only

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9
Q

Define coordination number

A

the total number of coordinate bonds formed between a central metal ion and ligands

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10
Q

What is the overall charge of a complex ion?

A

the sum of the charges on the central metal ion and any ligands present

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11
Q

Describe the written formula of a complex ion e.g. [Cr(H2O)6]3+

A

square brackets used to group all of the parts of the complex ion together
ligand inside round brackets
overall charge of complex outside square brackets

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12
Q

Define monodentate ligand

A

a ligand that is able to donate 1 pair of e- to a central metal ion

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13
Q

Give 5 examples of monodentate ligands

A 
H2O:
\:NH3
\:Cl-
cyanide, :CN-
\:OH-
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14
Q

Define bidentate ligand

A

a ligand that can donate two lone pairs f e- to the central metal ion, forming two coordinate bonds

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15
Q

Give 2 examples of bidentate ligand

A 
1,2-diaminoethane
ethanedioate ion (oxalate ion)
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16
Q

What does the shape of a complex ion depend upon?

A

its coordination number

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17
Q

Six-coordinate complexes can form which shape?

A

octahedral

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18
Q

Four-coordinate complexes can form which 2 shapes?

A

tetrahedral

square planar

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19
Q

In which complex ions does a square planar shape occur?

A

in those of transition metals with 8

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20
Q

Describe cis-trans isomerism in octahedral complexes with monodentate ligands

A

4 of 1 type of ligand and two of another type of ligand

21
Q

Describe optical isomerism in octahedral complexes

A

contain 2 or more bidentate ligands

‘cis’ isomers only

22
Q

What are trans-isomers of octahedral complexes unable to show optical isomerism?

A

mirror image is exactly the same and can be superimposed

23
Q

Describe the role of cis-platin in cancer treatment?

A

forms a platinum complex inside of a cell which binds to DNA, preventing DNA replication
activation of the cell’s own repair mechanism leads to apoptosis

24
Q

Define ligand substitution

A

a reaction in which one or more ligands in a complex ion are replaced by different ligands

25
Q

What colour is [Cu(H2O)6]2+ as a solution?

A

pale blue

26
Q

What happens to [Cu(H2O)6]2+ upon small addition of NH3?

A

Cu(OH)2, copper (II) hydroxide forms

pale blue ppt

27
Q

What colour is [Cu(H2O)6]2+ as a solution?

A

pale blue

28
Q

What happens to [Cu(H2O)6]2+ upon small addition of NH3?

A

Cu(OH)2, copper (II) hydroxide forms

pale blue ppt

29
Q

What happens to [Cu(H2O)6]2+ in excess of NH3?

A

[Cu(NH3)4(H2O)2]2+
dark blue solution
4 ammonia ligands replace 4 of the water ligands

30
Q

What happens to [Cu(H2O)6]2+ upon small addition of NH3?

A

Cu(OH)2, copper (II) hydroxide forms

pale blue ppt

31
Q

What colour is [Cr(H2O)6]3+ as a solution?

A

violet

32
Q

What happens to [Cr(H2O)6]3+ upon small addition of NH3?

A

Cr(OH)3, chromium (III) hydroxide

grey-green ppt

33
Q

What happens to [Cr(H2O)6]3+ in excess of NH3?

A

[Cr(NH3)6]3+

dark purple solution

34
Q

What happens to [Cr(H2O)6]3+ in excess of NH3?

A

[Cr(NH3)6]3+

dark purple solution

35
Q

What colour is chromium (III) sulfate dissolved in water?

[Cr(H2O)5 SO4]+

A

green solution

36
Q

What happens to [Cu(H2O)6]2+ in conc. HCl?

A

[CuCl4]2-
yellow solution (if not carried out to completion intermediate = green)
tetrahedral shape
6 water ligands have been replaced by 4 chlorine ligands
chlorine ligands are larger in size so fewer can fit around the central Cu 2+ ion

37
Q

Describe ligand substitution with relation to haemoglobin

A

CO can bind by ligand substitution to form carboxyhaemoglobin (irreversible)
if CO conc is too high, transport of O2 is prevented - leading to death

38
Q

Define precipitation reaction

A

the formation of a solid from a solution during a chemical reaction

39
Q

When are precipitates often formed?

A

when two aqueous solutions are mixed together

40
Q

What happens to Cu 2+ on the small addition of OH- ?

A

Cu(OH)2

pale blue ppt

41
Q

What happens to Cu 2+ on the small addition of OH- ?

A

Cu(OH)2

pale blue solution -> pale blue ppt

42
Q

What happens to Cr 3+ on the small addition of OH- ?

A

Cr(OH)3

violet solution -> grey-green ppt

43
Q

What happens to Fe 2+ on the small addition of OH- ?

A

Fe(OH)2
iron (II) hydroxide
pale green solution -> green ppt

44
Q

What happens to Fe 3+ on the small addition of OH- ?

A

Fe(OH)3
iron (III) hydroxide
yellow/orange solution -> orange-brown ppt

45
Q

What happens to Mn 2+ on the small addition of OH- ?

A

Mn(OH)2
manganese (II) hydroxide
pale pink solution -> light brown ppt

46
Q

What happens to Cr 3+ upon an excess of OH- ?

A

[Cr(OH)6]3-

dark green solution

47
Q

What is significant about the reactions of Fe2+, Fe3+ and Mn2+ with aqueous ammonia?

A

they react in the same way as with aqueous sodium hydroxide, forming precipitates

48
Q

Standard electrode potentials can be used to explain _. The more positive the E⦵ value, the more likely equilibrium is to _ electrons, shift to the _ and undergo _.

A

redox reactions
gain
RHS
reduction

49
Q

Suggest why vanadium does not form ions in which vanadium has an oxidation state greater than +5?

A

only 5 e- in 4s and 3d sub-shells

Chemistry (31 decks)

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