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A Level Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

1
Q

Def of transition elements

A

d-block elements with stable ions that employ partially filled d sub-shells

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2
Q

What is the electron configuration of Ca

A

Ca= [Ar] 4s2

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3
Q

Electron configuration of Sc ion (be careful as doesn’t fit normal’

A

Sc = [Ar] 3d14s2

Sc3+ = [Ar] (the 3d1 and 4s2 are lost)
Therefore Sc is not a transition metal

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4
Q

Electron configuration of Zn ion (be careful as doesn’t fit normal)

A

Zn = [Ar] 3d104s2

Zn2+ = [Ar] 3d10
Therefore Zn is not a transition metal

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5
Q

Why do Cr and Cu not fit the trend of d block electron configuration
Why does this occur

A

Cr and Cu have only 1 electron in 4s orbital and one more in the 3d orbital
E.g
Cr = [Ar] 3d5 4s1
This is due to
Half full and full d_shell paired with half full s shell being more stable

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6
Q

Features of d-block elements

A

Variable oxidation states
Complex ion formation (often coloured)
Paramagnetism in ions (respond to magnets)
Catalytic activity (as elements and compounds)

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7
Q

Contents of complex ion (transition metals)

A

Central metal “ion” chelated (bound) by ligands

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8
Q

What are ligands

A

Neutral molecules like NH3 or H2O
Or
Anions like Cl-/CN-

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9
Q

What kind of bond is found in complex ions

A

Lone pair of e- on ligands forms dative bonds
(Typically 6 bonds so frequently octahedral)

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10
Q

Calculate overall charge on complex ion

A

Overall charge = charge on ions + charge on ligands

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11
Q

How do you name a complex cation
E.g [Fe(H2O)6]^2+

A

Prefix for ligands + name of ion + oxidation number of ions

E.g hex aqua iron (II)
6. H20. Fe. 2+

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12
Q

How to name a complex anion
E.g [Fe(CN)6]4-

A
  1. Change Fe to ferrite
    (Cu would be cuprate otherwise metal & -ate)
    Then
    Prefect for ligand + name of ion + oxidation number of ion

E.g hexa. Cyano. Ferrite (II)
6. CN- Fe. 2+

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13
Q

Why are transition metal complexes stable

A

Complexes are stable due to release of energy when the lone pairs of the ligands form bonds with the central ion

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14
Q

True or false
Ligands vary in bond strengths

A

True
Ligands vary in their bond strengths : e.g H2O - bad ; NH3/CN- - good

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15
Q

What does variations in ligand bond strength mean if another one is added

A

One ligand will displace another if the bond strength of the old ligand is less that the bond strength of the new ligand
(This is called ligand exchange)

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16
Q

Complete the equation

[Fe(H2O)6]2+ + 6CN-

A

[Fe(H2O)6]2+ + 6CN- <—> [Fe(CN)6]4- + 6H2O

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17
Q

Why are aqua transition metal complexes acidic (H+ donors)

A

The charge dense metal ions polarise the water molecules allowing them to be attacked by other water molecules
See notes for mechanism

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18
Q

What is the name of the process where aqua complexes donate H+ ions

A

Deproptonation
NOT LIGAND EXCHANGE - a water molecules has become a OH- ion in situ - no ligand exchange occurred

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19
Q

How does addition of NH3 cause deprotonation of transition metal complexes

A

NH3 + H2O <—> NH4+ + OH-
These OH molecules then undergo the same deprotonation reaction as H2O

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20
Q

Draw a ligand structure

A

See notes

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21
Q

Why are transition metals good at being catalysts

A

Transition metals exhibit the properties of having more than one oxidation state for each element and therefore can form several different compounds

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22
Q

Why do transition metals form coloured ion

A

The unfilled d-Subshell in transition metal ions means that electrons can absorb visible light and therefore present as different colours

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23
Q

What shapes can complex ions form

A

Octahedral: many hexaaqua complexes
E.g [Cu(H2O6]2+
Tetrahedral: many tetrachloro complexes
E.g CuCl4^2-
Square planar: complexes of Pt
E.g Pt(NH3)2Cl2

24
Q

True of false complexes can be steriosomers

A

True
Complexes can for cis-trans isomerism and optical isomerism

25
What is the cis-platin compound used for
Cis-platin used as an anticancer drug due to it working to bind to revealed bases stopping DNA replication
26
The ligand substitution reaction and colour change of the reaction between [Cu(NH3)4(H2O2)]^2+ AND [CuCl4]^2-
[Cu(NH3)4(H2O2)]^2+ **+** [CuCl4]^2- **—>** [Cu(H2O)6]^2+
27
The ligand substitution reaction and the colour change for the reaction of [Cr(NH3)6]^3+. AND. [Cr(H20)6]^3+
[Cr(NH3)6]^3+ **+** [Cr(H20)6]^3+ **—>**
28
29
Types of monodentate and bidentate ligands
Monodentate: - H2O, Cl- , NH3 Didentate: NH2CH2CH2NH2 (‘en’)
30
What are the types of shapes that a complex can be
- octahedral shape (6 bonds) - tetrahedral shape (4 bonds) - square planar shape (4 bonds)
31
Match up the complexes with their shapes
Octahedral: many hexaaqua complexes Coordination numbers of 6 E.g [Cu(H2O)6]2+ , [Fe(H2O)6]3+ Tetrahedral: many tetrachloro complexes Coordination numbers of 4 E.g CuCl4 2- , CoCl4 2- Square planar: complexes of Pt Coordination numbers of 4 E.g Pt(NH3)2Cl2
32
Draw an octahedral hexaaqua complex [Cu(H20)6]2+
See notes
33
Draw a square planar complex Pt(NH3)2Cl2
See notes
34
True or false Complexes can show different types of stereoisomerism
True, Complexes including those with 4 and 6 coordination complexes can show cis-trans isomers but some molecules can also display optical isomer
35
Describe the role of cis-platin as a medicine
The cis-platin acts as an anti-cancer drug due to the action of it binding to DNA exploded bases during DNA replication preventing cel division leading to destruction of the cancerous cell
36
37
Outline the colours of the different transition element compounds
See notes in the book and complete on the paper
38
Why do transition metals exhibit colour compounds
The colour of a solution is linked to the partially filled d-orbital of the transition metal ion. The colour of a solution can vary with different oxidation states
39
Examples of processes catalysed by transition metals
1) Haber Process - for the manufacture of ammonia from the reaction between nitrogen and hydrogen this reaction is catalysed by iron 2) Contact Process - for production of sulfur trioxide from the oxidation of sulfur dioxide This reaction is catalysed by Vanadium(V) Oxides V2O5 3) catalytic decomposition of hydrogen peroxide forming oxygen This reaction is catalysed by manganese (IV) Oide MnO2
40
41
Def of ligands
A molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond or dative covalent bond
42
Def of coordination number
The number of coordinate bonds attached to the central metal ion
43
Examples of monodentate ligand with formula and charge
Water (H2O: ) - neutral Ammonia ( :NH3) - neutral Chloride (Cl:- ) - negative 1 Cyanide ( :CN-) - negative 1 Hydroxide ( :OH-) - negative 1
44
Examples of Bidentate ligands and what are they
Bidentate ligands = ligands that can donate two lone pairs of electrons to the central metal ion E.g 1,2-diaminoethane Ethanedioate ion (dicarboxylic acid but with H removed to from ion)
45
Draw and colour of the cis-trans isomers of [Co(NH3)4Cl2]+
The cis isomer (with chlorine on the same side) Appears as a violet colour The trans isomer (with chlorine symmetrically positioned) Appears as a green colour
46
Def of ligand substitution reaction
A reaction is one in which one ligand in a complex ion is replaced by another ligand
47
What is the reaction of copper(II) sulfate with excess ammonia And what is the colour change [Cu(H2O)6]2+ ..
[Cu(H2O)6]2+ **+** 4HN3 **—>** [Cu(NH3)4(H2O)2]2+ **+** 4H2O Pale blue solution. Dark blue solution But a pale blue precipitate Cu(OH)2 first produced then dissolves in excess ammonia to form a dark blue solution
48
Ligand substitution reaction of [Cu(H2O)6]2+ with HCl (chlorine ions) And what is the colour change
[Cu(H2O)6]2+ **+** 4Cl- **<—>** [CuCl4]2- **+** 6H2O Pale blue solution. Yellow solution The pale blue solution appears to at first turn green as a mixture of the yellow and blue solutions but as more Cl is added then solution completely turns yellow
49
50
Reactions of chromium (III) ions - dissolved as chromium (III) potassium sulfate in water - chromium (III) sulfate is dissolved in water
- KCr(SO4)2.12(H2O) Is dissolved in water the complex ion [Cr(H2O)6]3+ is formed This is a pale purple solution When chromium (III) sulfate It dissolves to form a green solution As instead of the [Cr(H20)6]3+ the complex ion [Cr(H2O)5SO4]+
51
Ligand substitution reaction of [Cr(H2O)6]3+ and ammonia Colour change that occurs
[Cr(H20)6]3+ **+** 6NH3 **—>** [Cr(NH3)6]3+ **+** 6H2O Violet solution. Purple solution In this reaction Initially a grey green precipitate of Cr(OH)3 forms The Cr(OH)3 precipitate dissolves in excess ammonia to form the complex ion [Cr(NH3)6]3+
52
Why is carbon monoxide toxic to haemoglobin
If carbon monoxide is breathed in, a ligand substitution reaction takes place where the oxygen in haemoglobin is replaced by carbon monoxide. Carbon monoxide binds to Hb more strongly than oxygen, this bond is so strong that this process is irreversible so cannot be unbound
53
Which reactants react generally with transition metals to make precipitations
Transition metal ions in aqueous solution react with 1) aqueous sodium hydroxide 2) aqueous ammonia To form precipitates However some of these precipitates will dissolve in an excess of sodium hydroxide or ammonia to from a complex ion in solution
54
Observation of these with NaOH - Cu2+ - Fe2+ - Fe3+ - Mn2+
-Cu2+ Blue solution reacts to form a **blue precipitate** of copper hydroxide -Fe2+ Pale Green solution reacts to form a **green precipitate** of iron (II) hydroxides This will turn brown in air as oxidised into iron (iii) - Fe3+ Pale yellow solution reacts to form an orange brown precipitate of iron(III) hydroxide - Mn2+ Pale pink solution reacts to form a light brown precipitate of manganese (II) hydroxide
55

A Level Chemistry (15 decks)

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