U1: Topic 4 Transition metals Flashcards
What are d-block transition metals?
Metals with an incomplete d sub shell in at least one of their ions.
Why do chromium and copper not follow Aufbau principle?
1/2 filled and completely filled sub shells are very stable and so are preferred energetically.
Uncombined elements have what oxidation state?
0
Ions containing single atoms have an oxidation state that is the same as?
Charge on the ion.
Sum of all oxidation states of all atoms in a molecule or neutral ion must add up to?
0
The sum of all oxidation numbers of all the atoms in a polyatomic ion must be equal to?
Overall charge on ion.
How is it easy for the 3d electrons to be lost when changing oxidation state?
Because 3d energy levels are close to that of the 4s so 3d electrons lost easy to form other oxidation states.
Oxidation states can be used to determine what?
Whether oxidation or reduction has happened.
An increase in oxidation state shows what?
Oxidation has occurred.
A decrease in oxidation state shows what?
Reduction has occurred.
It is usually true that high oxidation state compounds tend to be …. and low oxidation state compounds are….?
Oxidising agents
Reducing agents
What is a complex?
Metal ion surrounded by ligands.
A ligand is an electron ….?
Donor
Ligands are negative ions or molecules with what?
Non-binding pairs of electrons that they can donate to the central metal ion.
What type of bond do ligands form with the metal?
Dative covalent bonds.
Examples of common ligands.
Water
cyanide ions
ammonia
hydroxide ions
halide ions
oxalate ions
Ligands are classified according to how many pairs of electrons they donate examples…
Monodentate : one pair of
Bidentate : two pairs
Tridentate : three pairs
What is the coordination number?
Total number of bonds from ligands to central transition metal.
What is EDTA?
Common ligand used in complexometric titrations to determine quantities of metal ions in a substance. Complexes with metal ions in a 1:1 ratio.
In what order should complexes be named?
Ligand (alphabetical)
prefix placed infront (di, tetra)
metal named (negative charge add ate to end)
roman numerals
Transition metal complexes are named according to what rules?
IUPAC
In a complex of transition metals the d orbitals are no longer what ?
Degenerate
What causes the splitting of d orbitals to higher or lower energies?
Electrons present in approaching ligands cause electrons in the orbitals lying along the axes to be repelled.
Ligands that cause a large difference in energy between subsets of d orbitals are ….?
Strong field ligands.
Weak field ligands cause what?
Small energy difference.
What is the spectrochemical series?
Ligands placed in order of their ability to split d orbitals.
What is the spectrochemical series?
Ligands placed in order of their ability to split d orbitals.
Colours of many transition metal complexes can be explained by?
d-d transitions
When is light absorbed?
When electrons in a lower energy d orbital are promoted to a d orbital of a higher energy.
If light of one colour is absorbed then what colour with be observed?
The complementary colour.
When do electrons transition to higher energy levels?
When energy corresponding to the uv or visible regions of the electromagnetic spectrum is absorbed.
Transition metals and their compounds can act as what?
Catalysts
Heterogeneous catalysts are in a …..?
Different state to reactants.
Heterogeneous catalysts can be explained in terms of?
Formation of activated complexes and adsorption of reactive molecules onto active sites.
The presence of unpaired d electrons or unfilled d orbitals allows activated complex to form
Provides reaction pathways with lower activation energies compared to uncatalysed reaction.
Homogeneous catalysts are in the ….?
Same state as reactants.
Homogeneous catalysis can be explained in terms of?
Changing oxidation states with the formation of intermediate complexes.
