A-Level Chemistry (OCR) > 5.6 Transition Elements > Flashcards

5.6 Transition Elements Flashcards

Explain properties of transition metals using electronic structure and complex ion chemistry. (95 cards)

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1
Q

What feature of their electronic structure gives transition metals their characteristic properties?

A

Incomplete d sub-shell

Transition metals have partially filled d orbitals in atoms or ions.

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2
Q

What type of species is formed when a transition metal ion bonds with surrounding ligands?

A

Complex

A complex contains a central metal ion surrounded by ligands.

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3
Q

Fill in the blank:

A species that donates a pair of electrons to a metal ion to form a coordinate bond is called a _______.

A

ligand

Ligands act as Lewis bases when bonding to metal ions.

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4
Q

True or False:

Transition metal ions commonly form coloured compounds.

A

True

Colour arises from electronic transitions within d orbitals.

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5
Q

What property allows transition metals to exist in multiple oxidation states?

A

Variable oxidation states

The energies of 3d and 4s electrons are similar.

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6
Q

True or False:

Transition metals are often effective catalysts in chemical reactions.

A

True

They provide alternative reaction pathways with lower activation energy.

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7
Q

Fill in the blank:

The number of coordinate bonds attached to the central metal ion is called the _______ number.

A

coordination

Typical values include 4 or 6 in many complexes.

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8
Q

What type of bond forms when a ligand donates a lone pair to a metal ion?

A

Coordinate bond

Also called a dative covalent bond.

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9
Q

True or False:

Complex formation is a characteristic property of transition metals.

A

True

Ligands readily bind to transition metal ions forming complexes.

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10
Q

Why do transition metal ions often appear coloured in solution?

A

d–d electron transitions

Electrons absorb visible light to move between d orbitals.

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11
Q

Fill in the blank:

A complex consists of a central metal ion surrounded by _______.

A

ligands

These ligands donate electron pairs to form coordinate bonds.

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12
Q

What range of elements in the Periodic Table are commonly considered transition metals in A-level chemistry?

A

Ti to Cu

These elements show the typical transition metal properties in this specification.

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13
Q

What type of reaction occurs when one ligand in a complex is replaced by another?

A

Substitution reaction

A ligand attached to the metal ion is replaced by another ligand.

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14
Q

What term describes ligands that form only one coordinate bond to a metal ion?

A

Monodentate

Examples include H2O, NH3 and Cl-.

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15
Q

Fill in the blank:

Water, ammonia and chloride ions act as _______ ligands.

A

monodentate

Each forms one coordinate bond with the metal centre.

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16
Q

True or False:

Ligand substitution between NH3 and H2O usually occurs without changing the coordination number.

A

True

These ligands are similar in size and both are neutral.

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17
Q

What type of ligand forms two coordinate bonds to a metal ion?

A

Bidentate

It attaches to the metal ion at two donor atoms.

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18
Q

True or False:

Ethane-1,2-diamine (H2NCH2CH2NH2) is a bidentate ligand.

A

True

It has two nitrogen atoms that donate lone pairs.

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19
Q

Fill in the blank:

A ligand that forms several coordinate bonds to a metal ion is called _______.

A

multidentate

EDTA4- is a common example.

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20
Q

What name is given to the increased stability when multidentate ligands replace monodentate ligands?

A

Chelate effect

This occurs because several bonds form between one ligand and the metal.

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21
Q

True or False:

Chloride ligands are larger than water and ammonia ligands.

A

True

Their larger size can change the coordination number in some complexes.

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22
Q

What metal ion in haemoglobin binds oxygen through a coordinate bond?

A

Iron(II)

The Fe2+ ion in haem binds O2 reversibly.

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23
Q

Fill in the blank:

Carbon monoxide is toxic because it replaces _______ bound to Fe2+ in haemoglobin.

A

oxygen

CO binds more strongly than O2 to the iron centre.

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24
Q

Why are complexes with multidentate ligands often more stable than those with monodentate ligands?

A

Entropy increase

Replacing several ligands with one multidentate ligand increases disorder in solution.

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25
What is the most common **shape** of **transition metal complexes** with small ligands such as H2O and NH3?
Octahedral ## Footnote These complexes usually have coordination number 6.
26
What is the typical **coordination number** of an **octahedral complex**?
Six ## Footnote Six ligands surround the central metal ion.
27
# Fill in the blank: Transition metal ions often form _\_\_\_\_\_\_ complexes with **larger ligands** such as Cl-.
tetrahedral ## Footnote Larger ligands reduce the number that can fit around the metal ion.
28
# True or False: **Tetrahedral complexes** typically have a **coordination number of 4**.
True ## Footnote Four ligands are arranged around the central metal ion.
29
What **geometric shape** is commonly formed by some transition metal complexes with **coordination number 4**?
Square planar ## Footnote These complexes can show cis–trans isomerism.
30
# True or False: **Octahedral complexes** can show **cis–trans isomerism** when monodentate ligands are present.
True ## Footnote Different ligand positions create geometrical isomers.
31
# Fill in the blank: **Optical isomerism** in octahedral complexes commonly occurs when _\_\_\_\_\_\_ ligands are present.
bidentate ## Footnote These ligands can create non-superimposable mirror images.
32
What type of **stereoisomerism** produces **non-superimposable mirror image molecules**?
Optical isomerism ## Footnote These isomers rotate plane-polarised light.
33
# True or False: **Cisplatin** is the **cis isomer** of a square planar platinum complex used in cancer treatment.
True ## Footnote The cis arrangement allows it to bind effectively to DNA.
34
What is the **shape** of the complex ion **[Ag(NH3)2]+** used in Tollens’ reagent?
Linear ## Footnote The coordination number is 2.
35
# Fill in the blank: In a **cis isomer**, identical ligands are positioned _\_\_\_\_\_\_ each other.
adjacent ## Footnote In the trans form they are opposite each other.
36
What type of **isomerism** involves ligands being **opposite each other** in a complex?
Trans isomerism ## Footnote It is the opposite arrangement to the cis form.
37
Why do many **transition metal ions** appear **coloured in solution**?
d–d electron transitions ## Footnote Electrons absorb visible light and move between d orbitals of different energies.
38
What happens to **d electrons** when a transition metal ion **absorbs visible light**?
Excited to higher energy level ## Footnote The electrons move from a ground state to an excited state.
39
# Fill in the blank: The **colour observed** from a transition metal ion is due to _\_\_\_\_\_\_ wavelengths of light being absorbed.
specific ## Footnote The remaining wavelengths are transmitted or reflected.
40
# True or False: The **colour seen in a solution** corresponds to the **wavelengths of light that are absorbed**.
False ## Footnote The colour observed is the complementary colour of the absorbed light.
41
What **equation** relates the **energy absorbed by an electron** to the wavelength of light?
∆E = hv = hc/λ ## Footnote This equation links energy with frequency and wavelength of light. This equation is called planks constant
42
# True or False: Changing the **ligand** around a transition metal ion can change the **colour of the complex**.
True ## Footnote Different ligands change the energy gap between d orbitals.
43
# Fill in the blank: A change in _\_\_\_\_\_\_ state can alter the colour of a transition metal ion.
oxidation ## Footnote Different oxidation states alter the electronic environment.
44
What **experimental technique** measures how much **light a coloured solution absorbs**?
Spectroscopy ## Footnote It analyses absorption of electromagnetic radiation.
45
# True or False: A **colorimeter** can be used to determine the **concentration of coloured ions** in solution.
True ## Footnote Absorbance is proportional to concentration.
46
# Fill in the blank: A **graph used in colorimetry** often plots absorption against _\_\_\_\_\_\_.
concentration ## Footnote This calibration curve allows unknown concentrations to be determined.
47
What happens to the **energy difference between d orbitals** when **ligands change**?
It changes ## Footnote This alters the wavelength of light absorbed and therefore the colour observed.
48
What **property of transition metal ions** allows them to be **identified visually in solution**?
Characteristic colour ## Footnote Each metal ion often forms complexes with distinctive colours.
49
What **property** allows **transition metals** to form ions with different charges?
Variable oxidation states ## Footnote This occurs because the 3d and 4s electrons have similar energies.
50
Why can **transition metals** easily show **multiple oxidation states**?
Similar energy of 3d and 4s orbitals ## Footnote Electrons can be removed from both subshells.
51
# Fill in the blank: Transition metals can lose different numbers of electrons because their _\_\_\_\_\_\_ and 4s orbitals have similar energies.
3d ## Footnote This allows formation of several stable oxidation states.
52
# True or False: **Transition metals** typically exist in only **one oxidation state**.
False ## Footnote Many transition metals exhibit several oxidation states.
53
Which **metal ion** in **Tollens’ reagent** is reduced to form a silver mirror?
Silver(I) ## Footnote The complex ion [Ag(NH3)2]+ is reduced to Ag(s).
54
# True or False: **Tollens’ reagent** is used to distinguish **aldehydes from ketones**.
True ## Footnote Aldehydes reduce Tollens’ reagent to metallic silver.
55
# Fill in the blank: In the **Tollens’ test**, aldehydes are _\_\_\_\_\_\_ while silver ions are reduced.
oxidised ## Footnote The aldehyde is oxidised to a carboxylate ion.
56
What **reducing agent** is used to convert **vanadate(V) ions** to lower oxidation states in acidic solution?
Zinc ## Footnote Zinc reduces V(V) to V(IV), V(III) and V(II).
57
# True or False: The **colour of vanadium ions** changes as their **oxidation state** changes.
True ## Footnote Each oxidation state has a distinct colour in solution.
58
Which **oxidising agent** is commonly used in **redox titrations with Fe2+ ions**?
Permanganate ion ## Footnote MnO4- acts as a strong oxidising agent in acidic solution.
59
# Fill in the blank: In **permanganate titrations**, MnO4- is reduced to Mn2+ in _\_\_\_\_\_\_ solution.
acidic ## Footnote The purple permanganate ion becomes colourless Mn2+.
60
What **analytical technique** uses **redox reactions** to determine the concentration of a substance in solution?
Redox titration ## Footnote The volume of titrant used allows calculation of the amount of substance.
61
What type of **catalyst** is in a different **physical phase** from the reactants?
Heterogeneous catalyst ## Footnote The reaction occurs on the surface of the solid catalyst.
62
Where do **reactions occur** on a **heterogeneous catalyst**?
Active sites ## Footnote These are specific sites on the catalyst surface where reactants adsorb and react.
63
# Fill in the blank: Increasing the **surface area** of a heterogeneous catalyst increases the number of _\_\_\_\_\_\_ sites.
active ## Footnote More active sites allow more reactant molecules to react simultaneously.
64
# True or False: In a **homogeneous catalyst system**, the catalyst and reactants are in the **same phase**.
True ## Footnote Often both are dissolved in solution.
65
What **industrial process** uses **V2O5** as a catalyst?
Contact process ## Footnote V2O5 catalyses the oxidation of SO2 to SO3.
66
# True or False: **Iron** acts as a **heterogeneous catalyst** in the Haber process.
True ## Footnote It catalyses the reaction between nitrogen and hydrogen to form ammonia.
67
# Fill in the blank: Impurities that reduce **catalyst efficiency** by blocking active sites are called catalyst _\_\_\_\_\_\_.
poisons ## Footnote Catalyst poisoning reduces reaction efficiency and increases cost.
68
Why are **transition metals** effective **catalysts**?
Variable oxidation states ## Footnote They can easily gain and lose electrons during the reaction.
69
# True or False: In **homogeneous catalysis**, the reaction often proceeds through an **intermediate species**.
True ## Footnote The catalyst forms temporary intermediates during the reaction mechanism.
70
What **ion** catalyses the reaction between **iodide ions and peroxodisulfate ions**?
Fe2+ ## Footnote The Fe2+/Fe3+ redox pair acts as a catalyst.
71
# Fill in the blank: Mn2+ ions act as an _\_\_\_\_\_\_ catalyst in the reaction between C2O42- and MnO4-.
autocatalyst ## Footnote A product of the reaction catalyses the reaction itself.
72
What **advantage** does a **support medium** provide for heterogeneous catalysts?
Increased surface area ## Footnote It spreads the catalyst over a large surface, improving efficiency and reducing cost.
73
Give an example of **incomplete substitution** in ligand exchange
in [Cu(NH3)4(H2O)2]²⁺ only 4 water ligands are replaced by NH3, leaving 2 water ligands still attached
74
What is haem?
Haem is an iron(II) complex with a multidentate ligand ## Footnote The multidentate ligand is porphyrin
75
What factors affect the **oxidation state of a transition metal**?
* pH * The ligand attached
76
What is the **reduction half equation for MnO₄⁻ in acidic conditions**?
MnO₄⁻ + 8H⁺ + 5e⁻ → Mn²⁺ + 4H₂O ## Footnote MnO₄⁻ is reduced to form Mn²⁺ which acts as an autocatalyst for the reaction.
77
What is the **colour change of MnO₄⁻ in titrations**?
Purple → colourless
78
Why does **MnO₄⁻ act as its own indicator**?
Because it is intensely purple and becomes colourless when reduced
79
What is the **endpoint of a MnO₄⁻ titration**?
First permanent pale pink colour
80
What is the **half equation for oxalate oxidation**?
C₂O₄²⁻ → 2CO₂ + 2e⁻
81
Why is the **oxalate titration warmed**?
To increase reaction rate (it is slow at room temperature) ## Footnote Slow because MnO₄⁻ and C₂O₄²⁻ are both negative so repell
82
What property allows transition metals to be **good catalysts**?
variable oxidation states ## Footnote They allow transition metals to gain and lose electrons easily, enabling them to act as electron carriers and form intermediate species, lowering activation energy.
83
What reaction is catalysed by **V₂O₅** in the **Contact process**?
SO₂ + ½O₂ → SO₃
84
Write the **reduction step of V₂O₅ in the Contact process**?
V₂O₅ + SO₂ → V₂O₄ + SO₃
85
Write the **oxidation step regenerating V₂O₅ in the Contact process**.
V₂O₄ + ½O₂ → V₂O₅
86
Give the **equation** for the reaction **catalysed by Fe²⁺ ions between iodide and peroxodisulfate**?
S₂O₈²⁻ + 2I⁻ → I₂ + 2SO₄²⁻
87
What is the **first step** in **Fe²⁺ catalysis of S₂O₈²⁻ and I⁻**?
S₂O₈²⁻ + 2Fe²⁺ → 2SO₄²⁻ + 2Fe³⁺
88
What is the **second step** in **Fe²⁺ catalysis of S₂O₈²⁻ and I⁻**?
2Fe³⁺ + 2I⁻ → I₂ + 2Fe²⁺
89
What does **autocatalysis** mean?
A reaction where one of the products acts as a catalyst.
90
Which **ion** acts as the **autocatalyst** in the MnO₄⁻ and C₂O₄²⁻ reaction?
Mn²⁺
91
What is the **overall reaction between MnO₄⁻ and C₂O₄²⁻ in acidic conditions**?
2MnO₄⁻ + 5C₂O₄²⁻ + 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O
92
Why is the **MnO₄⁻** and **C₂O₄²⁻** reaction **slow** at first?
There is little Mn²⁺ present initially to act as a catalyst.
93
Why does the **MnO₄⁻** and **C₂O₄²⁻** reaction **speed up** over time?
Mn²⁺ is produced, which catalyses the reaction (autocatalysis)
94
What is the **first step involving Mn²⁺ and MnO₄⁻**?
MnO₄⁻ + Mn²⁺ → 2Mn³⁺ ## Footnote Mn²⁺ is oxidised to Mn³⁺, while MnO₄⁻ is partially reduced.
95
What happens to **Mn³⁺ when it reacts with oxalate**?
Mn³⁺ oxidises ethanedioate and is reduced back to Mn²⁺. ## Footnote Mn³⁺ + C₂O₄²⁻ → Mn²⁺ + 2CO₂
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