Transition Metals Flashcards
Where do the properties of transition metals come from
A partially filled D sub level in their atoms or ions
What are 4 characteristics of transition metals
Ability to form complexes
Form coloured ions
Variable oxidation states
Good catalysts
Why is zinc not a transition metal
It can only form a 2+ ions which gives it a completely filled d orbital so it doesn’t meet the criteria of being a transition metal
What is a complex
Transition metals or their ions forming Co ordinate bond with ligands
What is a ligand
A species that can donate one or more lone pair of electrons to a transition metal atom/ion
What is the co ordination number
The number of co ordinate bonds formed to a central metal ion
Shape and angle for 6 co ordinate bonds
Octahedral
90 degrees
Shape and angle for 4 co ordinate bonds (2)
Tetrahedral - 109.5
Square planar - 90
Shape and angle for 2 co ordinate bonds
Linear - 180
What is a monodentate ligand
Ligands that form one co ordinate bond with the metal ion
What are 4 monodentate ligands
H2O
Cl -
NH3
CN-
What is a bidentate ligand
Ligands that can form 2 co ordinate bonds with a metal ion as they have 2 atoms with lone pairs
What are 2 bidentate ligands
(Draw them out)
Ethane-1,2-diamine (en)
Ethanedioate ion
What are multidentate ligands
Ligands that can form 3 or more co ordinate bond with a metal ion
What is an example of a multidentate ligand and how many co ordinate bonds does it form
EDTA
Forms 6 co ordinate bonds
What 2 atoms have the lone pairs in EDTA
Oxygen and nitrogen
What is the structure of platin and cis platin
Draw
Square planar
Pt in middle
2 ammonia
2 cl
Swap based on isomerism
What types of isomerism can complexes form
Optical
Cis - trans
What is cis trans isomerism
A type of EZ isomerism
Cis = same side
Trans = opposite sides
When can optical isomerism in complexes
Octahedral complexes where there are 3 bidentate ligands to the central atom
What are the conditions for cis trans isomerism in square planar and octahedral complexes
2 of one ligand and 2 of another
4 of one ligand and 2 of another
What are 3 things that cause colour changes
Changes in
Oxidation state
Co ordination number
Ligand
Why do transition metals form coloured ions
They absorb energy corresponding to certain parts of the visible electromagnetic spectrum - the colour that is seen is made of the parts of the visible spectrum that aren’t absorbed
How does the colour change occur in terms of orbitals
In the presence of a ligand the d sub level can split orbitals - some into higher energies and some in lower
This changes energy and therefore the frequency of light absorbed
What is the link between change in E and the absorbing of colours
It it is small then it only absorbs the lower end of ROYGBIV
What are the 2 equations for change in E
Delta E = hf
Delta E = hc / wavelength
H is planks constant (6.63 x 10^-34)
F is frequency in Hz or s^-1
C is speed of light ( 3x10^18) m/s
What is the equation for C (speed of light)
Frequency x wavelength
Therefore delta E can also be hc / lander
What factors affect Delta E (4)
Type of ligand
Shape of complex
Co ordination number
Oxidation state of the metal
What is colourimetry
A type of spectroscopy
What light does colourimetry use
It uses ultraviolet to visible light
What is colourimetry used for
It is used to determine the concentration of transition metal ion complex solutions
How do you make a calibration graph (3)and how do you use it
Vary convention of sample
Measure absorbance at each concentration
Draw a graph of conc (x axis) against absorbance (y axis)
Measure absorbance of a sample and then use the graph to determine its concentration
What type of reaction is a ligand substitution reaction
What can it come with
When the metal ligand bond is broke. And replaced with a different ligand
Change in colour
Why does the co ordination number also change with chlorine ligand substitution reactions
Because chlorine is a bigger molecule that the other monodentate ligands
What is the reaction of aqueous copper chloride with HCl and what is the colour change
Cu(H20)6 2+ + 4HCl forms Cu(Cl)4 2- + 6H20
Blue to yellow/green
How is oxygen transported in the body
Blood has a multidentate ligand in complex called haem
one axial position bonds to globin (haemoglobin)
Othe axial position bonds to oxygen to form oxyhaemoglobin
When oxygen transported to tissues to bond breaks and is replaced by water in a partial Ligand sub reaction
Why is CO dangerous if inhaled
It bonds to the Fe 2+ on the axial
The bond is very strong so it can’t be broken therefore prevents oxygen from binding
High conc of co can be life threatening
What is entropy (delta S)
A measure of disorder in a system
What is an increase in entropy
A positive entropy change
What is delta G
What does it have to be for a spontaneous reaction to occur
Gibbs free energy
Negative
What is the equation for delay G
Delta G = DeltaH - T x DeltaS
Why ate monodentate ligand’s substituted by multidenatte
Why is it difficult to reverse the reaction
They form more stable complexes
There is an increase in entropy but delta h stays the same so g is negative
Requires a lot of energy cos backwards reaction would require DELTG to be positive but for a spontaneous reaction it has to be negative
Why is enthalpy of ligand substitution reactions 0 or almost 0
Breaking and forming the same type of bonds usually
What 4 oxidation states can Vanadium have
+5
+4
+3
+2
+1
What is the ion and colour of +5 vanadium
VO_2 +
Yellow
What is the ion and colour of + 4 Vanadium
VO^2+
Blue
What is the ion and colour of +3 vanadium
V3+
Green
What is the ion and colour of +2 vanadium
V^2+
Purple
What can vanadium be reduced by
Adding zinc
What characteristic of transition metals makes them good catalyst
Variable oxidation states
What is the overall equation for the contact process
What is the catalyst
What type or catalyst is it
SO2 + 0.5O2 (g) (RVs)-> SO3 (g)
V2O5
Heterogenous
What are the 2 equations showing how the catalyst in the contact process is used and reformed
SO2 + V2O5 -> SO3 + V2O4
V2O4 + 0.5O2 -> V2O5
What is a heterogenous catalyst
Catalysts that are in a different state to the reactants - usually catalyst is solid and reactants are gas or in solution
Why is a support used in heterogenous catalysis
The reaction takes places on the surface of the catalyst so a support increases the surface area which reduces costs
What are 3 stages of heterogenous catalysis
Reactants adsorb and form weak interactions with the surface
They weaken the bond between reactants so they become easier to break
Products desorb from the surface
What is homogenous catalysis
Catalysts in the same phase as the reactants usually in aqueous phase
How to homogeneous catalysts work
They reaction proceeds by an intermediate species in which the transition metal temporarily changes oxidation state
What happens when a catalyst is poisoned
Give 2 examples
When it is positioned by impurities which reduce the efficiency
For example sulfur in Haber process
Lead in catalytic converters
Why can’t leaded petrol be used in cars with catalytic converters
The lead strongly adsorbs to the surface of the catalysts
Steps of Fe2+ catalyst
For S2O8- and I- reaction
Why is reaction slow uncatalysted
Picture
Reacting 2 negative ions - they repel
Draw a diagram of enthalpy cos reaction progress
Photo
What is autocatalysis
When one of the products of the reactions acts as a catalyst in the reaction
Draw a diagram of mno4- vs time showing autocatalysis in its reaction with C2O4-
Explain it
Picture
Reaction speeds up once mn2+ is formed
Then evens out as reactants used up
Give the equations for mno4- reacting with c2o4-
Picture
What type of reaction is the reaction between sodium hydorxide and the metal ions
Hydrolysis reaction
What is the reaction of 2+ aqua ions with NaoH
Aquaion + 2OH- forms aqua ion (4) (oh)2 + 2H20
What is the colour change for age2+ aqua ion when it reacts with NaOH
Pale green solution
Green precipitate
Fe(h20)4(oh)2
Colour change for Cu2+ aqua ion reacting with NaOH
Blue solution - blue precipitate
Cu(H20)4(OH)2
What do +3 ions form when reaction with NaOH
Metal with 3 water molecules, 3 OH
And 3 H20
What does aluminium aqua ion form with NaOH
What about in excess
Colourless to white ppt
Ppt dissolves to form colourless solution
Al(oh)6 - + 3H2O
What is formed when 2+ metals reacts with ammonia
Metal with 4 ammonia and 2NH4+
What is the colour change for the reactions of 2+ aqua ions with ammonia
Same as with NaOH
Same products formed
Which is the only one that reacts with excess ammonia
What type do reaction is it
What is the colour change
What is the shape
Hexa aqua copper
A ligand substitution reaction
Cu(h20)4(oh)2 + 4Nh3 -> Cu(nh3)4(H2O)2 2+ + 2H20 + 2OH-
Blue precipitate to deep blue solution
Elongated octahedral because Cu-O bonds longer than C-N bonds
What is formed when 3+ ions react with ammonia
They react with 3 ammonia instead of 2
They form metal (h20)3(oh)3 and 3nh4+
What is the colour ur change for aqua fe3+ reacting with ammonia
Yellow/brown solution to brown ppt
Colourless solution to white ppt
Colour change when fe3+ reacts with naoh
Yellow/ brown solution to brown ppt
What is the reaction of 3+ aqua ions with carbonate
2 of the ions reacts with 3 carbonates.
To form 2 of metal(h20)3(oh)3 and 3H20 and 3CO2
What is the colour change and observation when fe3+ reacts with carbonate
Yellow brown solution to brown ppt and fizzing
Colour change and observation when Al3+ aqua ion reacts with carbonates
Colourless solution to white ppt
Fizzing
What is the reaction when carbonates react with 2+ aqua ions
One aqua ion with one carbonate ion forms Metal CO3 and 6H20
Reaction of Fe2+ aqua ion with carbonate
Pale green solution to green ppt
Reaction to Cu2+ aqua ion with carbonate
Blue solution to blue/green ppt
Why do only the +3 complexes cause fizzing with carbonates
The O-H bond is weak enough for carbonate ions to remove the H+ from the water ligands
Why is the O-H bond weaker in 3+ ions
They have a higher charge density so they attracts a pair of electron int he metal - oxygen bond towards itself more strongly which weakens the O-H bond
What is an example of a linear complex
Ag(NH3)2 2+
Cu(NH3)2 2+
