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chemistry a level > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

Where are transition metals on the periodic table

A

They are in the middle of the periodic table
Some of these transition metals.
The ones that you mainly need to know are the ones on the top row

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2
Q

What determines the properties of a transition metal

A

The properties of the transition metals are due to the electon configuration

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3
Q

What makes a transition metal a transition metal

A

A transition metal is a d block element that can form at lest one stable ion with a partially fixed (incomplete) d sub shell

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4
Q

How many electrons can be held in the d sub shell

A

The d sub sub shell can be hold up to 10 electrons

for period 4 d block elements only 8 of these are transition elements

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5
Q

Why are zinc and scandium NOT transition elements

A

They don’t form a stable ion with a partially filled d sub shell

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6
Q

What two transition metals that deviate from the trend

A

Chromium and copper behave differently
An electronic from the 4s orbital moved into the 3d orbital to create a more stable half full or full 3d sub shell respectively

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7
Q

Why are scandium and zinc not transition metals

A

Scandium forms 1 stable ion of Sc3+
Sc+3 has an empty d sub shell. As it is not partially filled, is is not a transition element

Zinc forms only 1 stable ion of Zn stable le ion of Zn2+ which has a full d sub shell.
As it is not partially filled it is nor a transition element

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8
Q

How does transition metals form ions

A

Transition metals lose electrons in a specific way to form ions
E.g. Fe3+ loses 3 elections 2 form 4s and 1 from 3d

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9
Q

What are the properties of transition metals

A

Variable oxidation states which forms coloured ions in solutions and they act as good catalysts (because of the varibake oxidation states)

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10
Q

Why do transition metals have variable oxidation states

A

Transition metals gave variable oxidation states.
This is because they’re electrons sit in 4s and 3d energy levels with are very close

As a result, electrons are gained and out using a similar amount of energy when they form the ions

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11
Q

What are the different ions of vanadium

A
  1. V2+ violet 2+
  2. V3+ green 3+
  3. VO2 2+ blue 4+
  4. VO2 + yellow 5+
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12
Q

What are the ions of chromium

A

Cr3+ 3+ green

Cr2O72- +5 orange

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13
Q

What are the coloured ions of manganese

A

Mn2+ pink

MnO4- purple

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14
Q

What is the coloured ions of nickel

A

Ni2+ green

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15
Q

What is the coloured ions of iron

A

Fe2+ pale green

Fe3+ yellow

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16
Q

What is the coloured ions in copper ions

A

Cu2+ blue

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17
Q

What is a complex ion

A

A complex ion is where a central transition metal ion is surrounded by liga ds binded by dative (coordinate) bonds

A property of transition metals is their ability to form complex ions

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18
Q

What are ligands

A

A ligand is an ion, atom ⚛ or a molecules that has at least 1 lone pair of electrons.

They can be monodente, bidente or polydente

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19
Q

How do we show coordinate honds

A

Coordinate bonds are shown with an arrow

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20
Q

What is a monodebte ligand

A

They are ligands that only have one lone pair of electrons are called mondente (unidente) ligands

Some examples of mondente ligands are:
H2O: water

:NH3 ammonia

:Cl- chloride ion

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21
Q

What is a bidente ligand

A

It is a ligand which have 2 lone pairs of electrons

Examples of bidente ligands:

Ethanediote

Ethane-1,2 diamine

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22
Q

What are multidente ligands

A

These are ligands which have more than 1 coordinate bond

Some examples:
EDTA4- which can does 6 coordinate binds with the central metal ion

Haem (from haemoglobin)

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23
Q

What does the complex shape depend on

A

The shape is dependant on the:

  • the size of the ligand
  • the coordination number
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24
Q

What is the coordination number

A

It is the number of coordinate bonds in a complex.

It is NOT the number of ligands

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25
Q

How many SMALL ligands can you fit around a central metal ion

A

You can fit 6 of them round a central metal ion

E.g. Water and ammonia

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26
Q

How many LARGE ligands can you fit around a central metal ion

A

You can for 4 of them around the central metal ion

Bidente ligands are even BIGGER so you van normally have 3 of these around a central metal ion

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27
Q

What is the shape of complexes with a coordination number of 6

A

They form octahedral shapes

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28
Q

What is the shape of complexes with a coordination number of 4

A

Complexesqith a coordination number of 4 form TETRAHEDRAL and SQUARE PLANAR shapes

A specific square planar complex is the anticancer drug cisplatin

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29
Q

What is the shape of complexes when they have a coordination number of 2

A

Complexes with a coordination number of 2 form linear shapes

A specific example are some silver complexes
E.g. Tollen’s reagent
Ag[(NH3)2]+ (aq)

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30
Q

Howdo we work out the oxidation state of a metal ion within a complex

A

The total oxidation state of the metal ion: total oxidation state - total oxidation state of the ligand

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31
Q

What is HAEM

A

Haem ks a multidete liga d that is found in the molecule haemoglobin

Haemoglobin is a protein used to transport O2 around the body in blood

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32
Q

What is HAEM

A

Haem ks a multidete liga d that is found in the molecule haemoglobin

Haemoglobin is a protein used to transport O2 around the body in blood

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33
Q

What is the structure of haemoglobinb

A

The structure of haemoglobin is ocatahedral

4 of the nitrogen ones from one multidente ligamd called haem

One of the coordinate bonds comes from a large protein card globin

The final coordinate bond comes either O2 or H2O

34
Q

How does hemoglobin work

A
  1. O2 substitutes the water ligands in the lungs where O2 concentration is high to form oxyhaemglobin.
    This transported around the body
  2. It goes to the place it is required where O2 and pick up H20 from the muscle. Haemoglobin returns back to the ground to start the process again
35
Q

What is carbon monoxide

A

Carbon monoxide is a lethal gas

It causes headaches, unconsciousness and even death.
It is known as the silent killer

36
Q

What happens to haemoglobin when carbon monoxide is inhaled

A

If carbon monoxide is inhaled the water ligand in the lungs/ going to the lunges is replaced with a carbon monoxide ligand

Unfortunately CO bond strongly do it’s not readiy replaced by oxygen or water

This means O2 can’t be transported and leads to O2 starvation in organs. Hence why CO is poisonous

37
Q

What is optical isomerism

A

They are non-superimposable mirror images of each other

Complex ions shows optical isomerism (a
type of stereoisomers)

38
Q

What is cis-trans isomerism

A

Complex ions also show Cis-trans isomerism (another type of stereosisomerism) which is a branch of E/Z isomerism

Octahedrals complexes with 4 ligands of the same type and 2 ligands of a different type display cis-trans isomerism

39
Q

What are trans isomerisms

A

If 2 different ligands are opposite each other you have a trans isomer

40
Q

What are cis isomers

A

If 2 ligands are adjacent to each other you have a cis isomer

41
Q

What isomerism can square planar isomers produce

A

Square planar complex with 2 ligands of the same type and 2 ligands of a different type displays cis trans isomerism

42
Q

What happens when the d orbitals split

A

The d sub shell is split into 2 when ligands bind with the central metal ion

E.g.
When ligands are attached some orbitals gain energy
An energy gap is created
When electrons absorb light some move
from the lowest power enegy level (ground state) to higher energy level orbitals (excited level)

In order for this to happen, you need a partially filled sub shell. If it was full they can’t move up or down

43
Q

What must the energy from light be equal to for the electrons to move up

A

In order for this to happen the energy from the light must be equal to THE ENERGY GAP ⃤E

44
Q

What is △E equal dependant on

A

The central metal ion and its oxidation state

They type of laignad

Coordination number

45
Q

How can we calculate the energy absorbed by the electrons

A

We can use this formula:
⃤E = hv = hc/λ

delta E is the cahneg jn energy (J)

v = the frequency of light absorbed on hertz

h= Plank’s constant

c = speed of light

λ= wavenght of light

46
Q

Absorbing visible light

A

Some frequencies of visible light are absorbed by transition netal complexes.

The frequencies absorbed depends on the size of delta E

e.g increasing frequency = the large the energy gap

47
Q

What happens to the frequencies that are not absorbed

A

Any frequencies which are not absorbed are reflected or transmitted

The combination of these reflected frequencies create a complementary colour that we observe with some complexes

E.g. [Cu(H2O)6]2+ absorbs frequencies that produce red light. The complementary colour is light bliss (cyan) so we observe this colour

48
Q

What happens when there is a complex where we have a full or empty 3d subshe

A

When we have a or empty 3d subshell no electros can migrate to the higher energy level.
This means we see these complexes as colourless or white e.g. zinc, scandium

49
Q

What are the factors that can effect the colour of a complex

A

Ligand substitution

There can be ligand substitution wbre the coordination number and the shape remains the same or when the coordinstion number changes (and as follows so does the shape)

This normally happens when a smaller ligand is subsituetd by a larger ligand like Cl-

Shape of complex

Oxidation state

50
Q

What is calorimetry

A

Transition metal complexes can be analysed using calorimetry.

The colours we see are compliments of the colours absorbed by the solution

51
Q

How does calorimetry

/spectroscopy work

A

Spectroscopy can be used to determine the concentration of a solution by measuring how much light it absorbs.
White light is shone through a filter which is chosen to only let the colour of light through that is absorbed by the sample

The light then passes through the sample to aq colourimeter, which shows how much the sample absorbed light. The more concentrated a coloured solution, the more light will absorb

52
Q

Hie cam we work out the concentration of an unknown sample

A

We then produce a calibration graph (or calibration curve) with concentration on the x and relative absorbance on the y

53
Q

What are transition metals substitution reaction

A

A colour change can exist when ligands in a complex substitute with a different ligand

These substitution reactions show how ligands
of a similar size being exchanged

E.g.
Partial substitution reactions occur when [Cu(H2O)6]2+ reactions with excess ammonia

54
Q

How can a Modentate ligand be formed by ligand substitution

A

Different ligands can form different strong bonds to the metal ion

E.g. CN-ion forms stronger bonds that the H2O molecules. This means this reaction js not easily reversed. The new complex formed is, therefore, more stable

The reaction that occurs is not easily reversed and the complex formed is more stable as a result

55
Q

What type of ligand forms stable complexes

A

Multidentate ligands form complexes that are more stabke than monodetate ligands

So it is harder to reverse the reaction

56
Q

What else can increase the stability of a complex

A

Increasing the entropy forms a more stable complex

In a ligand exchange bonds are broken in the original complex and new ones are formed go make the new complex.
Quite often rhe energy needed to break the binds is similar as the early released when the new ones are formed. Therefore the overall enthalpy change is small.

However the reaction is mot reversible due to entropy increasing which forms are table complex

57
Q

What is the increasing im stability called

A

The increasing in stablity is known as the CHELATE

58
Q

Why does entropy change in substitution monodente ligands with bidentate and multidendate ligands

A

This is because we create a solution with more particles in it.

This means we have an increase in entropy

Positive entropy change = more likely to happen

59
Q

When does redox reaction occur

A

A property of transition metals is that they can exist in variable oxidation states

When you switch between these oxidation states, a redox reaction occurs as the metal ions are either oxidised or reduced

60
Q

How can we reduce vanadium

A

Vandium can be reduced by adding it to zinc metal in an acidic solution

61
Q

What are redox potentials

A

Redox potentials of an ion or atom tell you how easy it is reduced to a lower oxidation state like electrode potentials

62
Q

The more positive the redox potentials […]

A

the less stable the ion will be and so the more likely it is to be reduced

63
Q

How do we get redox potentials

A

Redox potentials can be derived from standard electrode potential

These have been measured with the reactants at a concentration of 1 mol dm3 against a standard hydrogen electrode under standard conditions

However, the redox potentials of an ion won’t Aways be the same as its standard electrode potential. This is because it can vary with the environment the ion is in

64
Q

What are the different environments that effect redox potentials

A

Ligands present

pH effect

65
Q

How does the ligands effect redox potentials

A

Standard electrode potentials are measured in aqeous solutions so any ions will be surrounded by water ligands

Different ligands may make the redox potential larger or smaller depending on how well they bind to the metal ion in a particular oxidation state

66
Q

How does Ph effect redox potentials potentials

A

Some ions need H+ ions present in order to be reduced

Others release OH- ions into a solution when they are reduced

For reactions like these, the pH of the solution affects the redox potentials. In general the redox potentials will be more positive in more acidic solutions because the ions are more easily reduced

67
Q

What oxidation state does silver have

A

Silver is a transition metal that is most commonly found in +1 oxidation state

It is easily reduced to silver metal

It has a standard electrode potential of +0.8V

It is this reduction reaction that help to distinguish between aldehyde and ketones

68
Q

How do we prepare tollen’s reagent

A

We add just enough ammonia solution to silver nitrate solution to form a colourless solution contains the complex ion:
[Ag(NH3)]2 ]+

69
Q

What happens when we add tollens reagent to a solution containing an aldehyde

A

The aldehyde is oxidised to a caeboxylate abion and the Ag+ ions are reduced to silver metal

Tollens reagent can’t oxidise ketone, so it won’t react with them, and silver mirror will form

70
Q

What is the equation that occurs between snd aldehyde and tollens reagent

A

RCHO(aq) + 2[Ag(NH3)2]+ +OH- → RCOO-(aq) + 4Ag + 4NH3(aq) +2H2O

71
Q

What can we use redox titrations for

A

Tjtrations ca be used to work out the concentrations of a reducing or oxidising agents

72
Q

What are the steps involved with a redox titrations

A
  1. Have your reducing agent e.g. Fe2+solution with an unknown concentration but known volume in a conical flask

Make sure you add excess dilute sulfuric acid into this too. This js to ensure you have sufficient H+ ions to allow the eduction of oxidising agent

  1. have an oxiding agent in the burette with a known concentration
  2. add the oxidising ionsin the burette to the conceal flask until you see the faint colour of the agent appear.This known as the end point. Add drop by drop near the end point
  3. Stop when the mixture in the flask just becomes tained with the colour of the oxidinh agent and record the volume of the oxiding agent tasded. This is the rough titration
  4. Now do the accurate titrations. Repeat until you get two or more readings that are concordant to each other → within 0.10 cm3
73
Q

What are the different types of catalysts

A

Homogenous

Heterogenous

74
Q

what are heterogenous catalysts

A

this is a catalyst that is in a different phase from the reactants from the reactants

The catalyst is in a different state from the reactants

There are two types of heterogeneous catalysts:

  1. Iron
  2. vandium
75
Q

what are the two types of heterogeneous catalysts

A
  1. Iron
    which is used in the Haber Process for making ammonia

N2(g) + 3H → 2NH3

  1. Vandium (V) oxide
    that’s used in the content process
    SO2 + 1/2O2(g) → SO3 (g)

In all of these reactions, the catalyst is a solid and the reactants are gases.

These gases are passed over the solid catalyst

76
Q

what are homogeneous catalysts

A

they are in the same physical state as the reactants

usually a homogeneous catalyst is an aqueous catalyst for a reaction between two aqueous solutions

77
Q

how do homogeneous catalysts work

A

it works by forming an intermediate species

The reactants combine with the catalyst to make an intermediate species, which then reacts to form the products and reform the catalyst

This caused the enthalpy profile for a homogenously catalysed reaction to have two humps in it, corresponding to the reactions.
The activation needed to form the intermediates (and to form the products from the intermediates) us lower than that needed to make the products directly from the reactants

78
Q

what are the two homogenous catalysts that you need to know

A

Fe2+ catalysed the reaction between S2O82- and I-

this reaction is a redox reaction

Mn2+ autolcatatalysing the reaction between MnO4- and C2O42-

79
Q

why does the Fe2+ catalysed the reaction between S2O82- and I- slow and how does Fe catalyse the reaction

A

the reaction occurs slowly because both ions are negatively charged.
The ions repel each other, so it’s unlikely they’ll collide and react

But if Fe2+ ions are added, things are really speeded up because each stage of the reaction involves a positive and a negative ion, so there is no repulsion

first, the Fe2+ ions are oxidised to Fe3+ ions by the S2O82- ions

The newly formed intermediate Fe3+ ions now easily oxidise the I- ions to iodine and the catalyst is regenerated

80
Q

why is the second homogenous catalyst reaction an autocatalyse reaction

A

another example of a homogenous catalyst is Mn2+ in the reaction between C2O42- and MnO4-

It is an autocatalysis reaction because Mn2+ is a product of the reaction and acts as a catalyst for the reaction. This means that as the reaction progresses and the amount of the product increases, the reaction speeds up

81
Q

how does this reaction: Mn2+ autocatalysis the reaction between MnO4- and C2O42 work

A

There isn’t any Mn2+ present at the beginning if the reaction to catalyse it, so at first, the rate of reaction is very slow

During this uncatalysed part of the reaction, the activation energy is very high

This is because the creation proceeds via the collision of negative ions, which requires a lot of energy to achieve
But once a little bit of the manganate 2+ catalyst has been made it reacts with the MnO4- ions to make Mn2+ ions

chemistry a level (24 decks)

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