Topic 16-Transition Metals
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Electronic configuration of chromium
Ar 3d⁵ 4s¹
Electronic configuration of copper
Ar 3d¹⁰ 4s¹
Why do transition metals have variable oxidation states
Because electrons in the 3d and 4s subshell sit very close to each other So electrons are lost with a similiar amount of energy And: Transition metals have variable oxidation states as there is a gradual increase in the successive ionisation energies
What is a ligand and what bonding occurs between ligand at central metal ion
An ion metal or atom that has at least one lone pair of electrons Can be monodentate bidentate or polydentate They form coordination bond(dative covalent bond)
What is a complex ion
A central metal ion surrounded by ligands
Transition metals forms coloured compounds in solution
How doee transition metals form coloured compounds
The d subshell splits into 2 different energies when a ligand binds to a central metal ion Difference in energy depends on the ligand Difference in energy leads to different frequencies being absorbed and electrons move up energy levels So unabsorbed frequencies are transmitted
Why is there a lack of colour in some aqueous ions and complex ions
For complexes where we have a full or empty 3d subshell no electrons can migrate to a higher energy level This means we have colourless complexes
Explain how changing the oxidation no changes the colour of TM ion
Change in OS means change in effective nucleur charge affecting the energy gap between d orbitals Higher OS changes wavelength of light absorbed Shifts colour change
How does different ligands affect colour of TM ion
Different ligands cause Different Ligand field strength This affects wavelength of visible light from being absorbed changing the colour
How does coordination number affect colour of TM ion
Changing number of ligands coordinately bonded means geometry changes which changes the splitting of the d subshell Altering the colour
What happens when metal aqua ions of 2+ charge(Fe,Co,Cu) react with OH- in a partial ligand substitution reaction
They form a transition metal complex with 2 OHs and 4 H20s E.g [Fe(OH)2(H2O)4]
Cr³+ is the only metal aqua ion that will react in a full ligand substitution with OH- what is the transition metal complex formed And calculate charge of TM complex
[Cr(OH)6]^(-3) Charge equals 3-6= -3
What happens when metal aqua ions of 2+ charge(Fe,Co,Cu) react with NH3(not in excess) in a partial ligand substitution reaction
They form TM complexes with 2 OHs and 4 H2O and also 2NH4 E.g. [Fe(OH)2(H2O)4] + 2NH4
What 2 metal aqua ions react with excess NH3 in a full ligand substitution reaction and give an example
Cr³+ and Co²+ [Cr(NH3)6]
What happens when Cu²+ reacts with excess NH3
It forms: [Cu(NH3)4(H2O)2] Charge is 2+ as Ammonia and water have no charge
What is a metal aqua ion
A TM with 6 coordinate bonds of H20 E.g. [Fe(H2O)6]
What is the catalyst when 2SO2 + O2 → 2SO3
Vanadium oxide (V2O5)
State the intermediate reactions of SO2 + O2 → SO3 Using V2O5 catalyst
1) V2O5 + SO2 → V2O4 + SO3 2) V2O4 + 1/2O2 → V2O5 V2O5 catalyst regenerated
Which is the only TM ion that undergoes partial/incomplete ligand substitution in EXCESS NH3 State the colour and complex ion
Cu2+ Goes from Copper hexaaqua ion to [Cu(NH3)4(H20)2]2+ From blue to deep blue