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