Transition Metals Flashcards
Where are transition metals on the periodic table
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
What determines the properties of a transition metal
The properties of the transition metals are due to the electon configuration
What makes a transition metal a transition metal
A transition metal is a d block element that can form at lest one stable ion with a partially fixed (incomplete) d sub shell
How many electrons can be held in the d sub shell
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
Why are zinc and scandium NOT transition elements
They don’t form a stable ion with a partially filled d sub shell
What two transition metals that deviate from the trend
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
Why are scandium and zinc not transition metals
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
How does transition metals form ions
Transition metals lose electrons in a specific way to form ions
E.g. Fe3+ loses 3 elections 2 form 4s and 1 from 3d
What are the properties of transition metals
Variable oxidation states which forms coloured ions in solutions and they act as good catalysts (because of the varibake oxidation states)
Why do transition metals have variable oxidation states
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
What are the different ions of vanadium
- V2+ violet 2+
- V3+ green 3+
- VO2 2+ blue 4+
- VO2 + yellow 5+
What are the ions of chromium
Cr3+ 3+ green
Cr2O72- +5 orange
What are the coloured ions of manganese
Mn2+ pink
MnO4- purple
What is the coloured ions of nickel
Ni2+ green
What is the coloured ions of iron
Fe2+ pale green
Fe3+ yellow
What is the coloured ions in copper ions
Cu2+ blue
What is a complex ion
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
What are ligands
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
How do we show coordinate honds
Coordinate bonds are shown with an arrow
What is a monodebte ligand
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
What is a bidente ligand
It is a ligand which have 2 lone pairs of electrons
Examples of bidente ligands:
Ethanediote
Ethane-1,2 diamine
What are multidente ligands
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)
What does the complex shape depend on
The shape is dependant on the:
- the size of the ligand
- the coordination number
What is the coordination number
It is the number of coordinate bonds in a complex.
It is NOT the number of ligands
How many SMALL ligands can you fit around a central metal ion
You can fit 6 of them round a central metal ion
E.g. Water and ammonia
How many LARGE ligands can you fit around a central metal ion
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
What is the shape of complexes with a coordination number of 6
They form octahedral shapes
What is the shape of complexes with a coordination number of 4
Complexesqith a coordination number of 4 form TETRAHEDRAL and SQUARE PLANAR shapes
A specific square planar complex is the anticancer drug cisplatin
What is the shape of complexes when they have a coordination number of 2
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)
Howdo we work out the oxidation state of a metal ion within a complex
The total oxidation state of the metal ion: total oxidation state - total oxidation state of the ligand
What is HAEM
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
What is HAEM
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
What is the structure of haemoglobinb
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
How does hemoglobin work
- O2 substitutes the water ligands in the lungs where O2 concentration is high to form oxyhaemglobin.
This transported around the body - 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
What is carbon monoxide
Carbon monoxide is a lethal gas
It causes headaches, unconsciousness and even death.
It is known as the silent killer
What happens to haemoglobin when carbon monoxide is inhaled
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
What is optical isomerism
They are non-superimposable mirror images of each other
Complex ions shows optical isomerism (a
type of stereoisomers)
What is cis-trans isomerism
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
What are trans isomerisms
If 2 different ligands are opposite each other you have a trans isomer
What are cis isomers
If 2 ligands are adjacent to each other you have a cis isomer
What isomerism can square planar isomers produce
Square planar complex with 2 ligands of the same type and 2 ligands of a different type displays cis trans isomerism
What happens when the d orbitals split
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
What must the energy from light be equal to for the electrons to move up
In order for this to happen the energy from the light must be equal to THE ENERGY GAP ⃤E
What is △E equal dependant on
The central metal ion and its oxidation state
They type of laignad
Coordination number
How can we calculate the energy absorbed by the electrons
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
Absorbing visible light
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
What happens to the frequencies that are not absorbed
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
What happens when there is a complex where we have a full or empty 3d subshe
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
What are the factors that can effect the colour of a complex
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
What is calorimetry
Transition metal complexes can be analysed using calorimetry.
The colours we see are compliments of the colours absorbed by the solution
How does calorimetry
/spectroscopy work
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
Hie cam we work out the concentration of an unknown sample
We then produce a calibration graph (or calibration curve) with concentration on the x and relative absorbance on the y
What are transition metals substitution reaction
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
How can a Modentate ligand be formed by ligand substitution
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
What type of ligand forms stable complexes
Multidentate ligands form complexes that are more stabke than monodetate ligands
So it is harder to reverse the reaction
What else can increase the stability of a complex
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
What is the increasing im stability called
The increasing in stablity is known as the CHELATE
Why does entropy change in substitution monodente ligands with bidentate and multidendate ligands
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
When does redox reaction occur
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
How can we reduce vanadium
Vandium can be reduced by adding it to zinc metal in an acidic solution
What are redox potentials
Redox potentials of an ion or atom tell you how easy it is reduced to a lower oxidation state like electrode potentials
The more positive the redox potentials […]
the less stable the ion will be and so the more likely it is to be reduced
How do we get redox potentials
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
What are the different environments that effect redox potentials
Ligands present
pH effect
How does the ligands effect redox potentials
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
How does Ph effect redox potentials potentials
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
What oxidation state does silver have
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
How do we prepare tollen’s reagent
We add just enough ammonia solution to silver nitrate solution to form a colourless solution contains the complex ion:
[Ag(NH3)]2 ]+
What happens when we add tollens reagent to a solution containing an aldehyde
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
What is the equation that occurs between snd aldehyde and tollens reagent
RCHO(aq) + 2[Ag(NH3)2]+ +OH- → RCOO-(aq) + 4Ag + 4NH3(aq) +2H2O
What can we use redox titrations for
Tjtrations ca be used to work out the concentrations of a reducing or oxidising agents
What are the steps involved with a redox titrations
- 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
- have an oxiding agent in the burette with a known concentration
- 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
- 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
- Now do the accurate titrations. Repeat until you get two or more readings that are concordant to each other → within 0.10 cm3
What are the different types of catalysts
Homogenous
Heterogenous
what are heterogenous catalysts
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:
- Iron
- vandium
what are the two types of heterogeneous catalysts
- Iron
which is used in the Haber Process for making ammonia
N2(g) + 3H → 2NH3
- 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
what are homogeneous catalysts
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
how do homogeneous catalysts work
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
what are the two homogenous catalysts that you need to know
Fe2+ catalysed the reaction between S2O82- and I-
this reaction is a redox reaction
Mn2+ autolcatatalysing the reaction between MnO4- and C2O42-
why does the Fe2+ catalysed the reaction between S2O82- and I- slow and how does Fe catalyse the reaction
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
why is the second homogenous catalyst reaction an autocatalyse reaction
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
how does this reaction: Mn2+ autocatalysis the reaction between MnO4- and C2O42 work
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
