2.5 Transition Metals
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What is the definition of a Transition Metal?
Contain an incomplete d subshell
What is the definition of a ligand?
Particle with a lone pair which forms a coordinate bond
What is the definition of a complex?
Metal ions with ligands coordinately bonded
What are the four key properties of transition metals?
-Colourful - Complex ions - Variable oxidative states - Catalytic activity
What complex forms a linear shape?
Ag+
What causes complex to form tetrahedral shapes?
Large ligands e.g. Cl
What complex forms square planar shapes?
Pt 2+
What complexes form octahedral shapes?
Most complexes
What is a unidentate ligand?
A ligand which only forms one coordinate bond
What is a bidentate ligand?
Forms two coordinate bonds
What is a multidentate ligand?
Ligand which forms more than two coordinate bonds
What stereoisomerism features do transition metal complexes display?
• Geometric isomerism (Cis-trans isomerism) • Optical isomerism
Why are complexes coloured?
• 5d orbitals split into two different energy levels so 1. d electrons absorb different frequencies of white light 2. d electrons get promoted to higher energy levels 3. Colour seen is light transmitted and not absorbed by moving electrons
What is the link between the concentration of a solution and light absorbed?
The more concentrated a solution the more light absorbed
What are the uses of variable oxidation states?
• testing for aldehydes • Oxidising alcohols • Catalysis • Redox titrations
What are the four different oxidation states of vanadium and what colour is each state?
VO2+ - 5+ (yellow) VO 2+- 4+ (blue) V 3+- 3+ (green) V 2+- 2+ (Violet)
Why is dilute H2SO4 used when reacting KMnO4?
H2SO4 needed as Cl- would be oxidised if HCl used Dilute because conc H2SO4 is an oxidising agent
What is the ratio when KMnO4 reacts with Fe2+?
5 Fe2+ : 1 MnO4-
What is the ratio when C2O42- reacts with MnO4-?
52O42- :2MnO4-
What is a heterogeneous catalyst?
Catalyst in different state than reactants
How do heterogeneous catalysts work?
At least 1 reactant is adsorbed onto surface
What is catalyst poisoning?
Substances bindin too strongly to active sites blocking them
Why do transition metals make good catalysts?
Variable oxidation states