Transition metals Flashcards
What block of the periodic table are the transition metals in?
-D block
What is a transition metal?
-A transition metal is a metal that can form one or more stable ions with an incomplete d sub-level
What are the physical properties of transition metals?
-High density
-High melting and boiling points
What are the chemical properties of transition metals?
-Can form complex ions
-Form coloured ions
-Good catalysts
-Variable oxidation states
What is a complex ion?
-A metal ion surrounded by co-ordinately bonded ligands
What is a dative (co-ordinate) bond?
-A covalent bond in which both electrons in the shared pair come from the same atom
What is a ligand?
-An atom, ion or molecule that donates a pair of electrons to a central metal ion
What are ligands that form more than one co-ordinate bond called?
-Multidentate
What are ligands that form only one co-ordinate bond called?
-Monodentate
How do you work out the oxidation state of the metal ion?
oxidation state=total charge of complex-sum of the charges of the ligands
How many lone pairs does EDTA^4- have?
6 lone pairs
What does bidentate mean?
-Multidentate ligands that can form two co-ordinate bonds
What determines the shape of a complex ion?
-Its co-ordination number
What are the two types of stereoisomerism?
-Optical isomerism
-Cis-trans isomerism
When does optical isomerism occur?
-When an ion can exist as two non-superimposable mirror images
What are optical isomers called?
-Enantiomers
What is cisplatin?
-A complex of platinum (II) with two chloride ions and two ammonia ions in a square planar shape
What are the uses of cisplatin?
-Can be used to treat some types of cancer
What is the equation used to figure out the energy absorbed when electrons jump?
energy change=hv=hc/*
h=Planck’s constant
v=Frequency of light absorbed (Hz)
c=Speed of light
*=Wavelength of light absorbed
What factors can change the colour of transition metals?
-Changes in oxidation states
-Changes in co-ordination number
-Changes in ligand
What is spectroscopy?
-Can be used to determine the concentration of a solution by measuring how much light it absorbs
What is ligand substitution?
-When one ligand is swapped for another
What happens when substitution of similarly sized ligands occurs?
-Co-ordination number of the complex ion doesn’t change
-Shape of complex ion doesn’t change
What happens when substitution of different sized ligands occurs?
-Change of co-ordination number
-Change of shape
What is the multidentate ligand in haemoglobin?
-Porphyrin
What happens to haemoglobin when carbon monoxide is inhaled?
-Water ligands are substituted for carbon monoxide ligands, forming carboxyhaemoglobin
Summarise the oxygen transport process
High conc of O2
-Oxygen displaces water to form oxyhaemoglobin
-Lungs->Bloodstream->Site where oxygen is needed
Low conc of O2
-Water displaces oxygen to form deoxyhaemoglobin
-Bloodstream->Lungs
What forms more stable complexes, multidentate ligands or monodentate ligands?
-Multidentate
What is the enthalpy change like during a ligand exchange reaction?
-Very small
What is the entropy change like during a ligand exchange reaction?
-Large increase
What is the chelate effect?
-When monodentate ligands are substituted with bidentate or multidentate ligands and the number of particles increases
What are the oxidation states and colours of the vanadium ions?
+5=Yellow
+4=Blue
+3=Green
+2=Violet
How can vanadium be reduced?
-adding zinc metal to it in an acidic solution
What is the redox potential of an ion or atom?
-How easily it is reduced to a lower oxidation state
What factors affect redox potential?
-Ligands
-pH
Why do transition metals make good catalysts?
-They can change oxidation states by gaining or losing electrons within their d orbitals
What is a heterogeneous catalyst?
-It is in a different state than the reactants
What is a support medium used for?
-To make the area of a catalyst as large as possible
What does catalyst poisoning do?
-Reduces the surface area of the catalyst available to the reaction
What is a homogeneous catalyst?
-In the same physical state as the reactants
