2.5 Transition Metals Flashcards
What are the properties of a transition metal?
3d Block Forms one or more stable ions which have partially filled d orbitals Forms complex ions Forms colour compounds Variable oxidation states Catalytic activity
What is a ligand?
A ligand is a molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons
What are examples of mono dentate ligands?
H2O
NH3
Cl-
What is the co-ordination number?
The total number of co-ordinat ends formed between the central ion and the ligand
What is a bidentate ligand?
Donates 2 lone pairs
H2NCH2CH2NH2
What is a multi dentate ligand?
Donates many lone pairs
EDTA -4
What are the shapes that ligands can find?
Linear
Square Planar
Tetrahedral
Octahedral
What are Cis/Trans Isomers?
A special case of E/Z isomers
What is Cisplatin?
An anticancer drug which binds to Guanine in DNA
H3N—-Pt—–NH3
Cl——- ——-Cl
What is Transplatin?
An isomer of Cisplatin which has no use in medicine as it is toxic
What is Haemoglobin?
Iron surrounded by Haem group
Hollow ring (Porphyrin) of carbon and hydrogen attached to N which donates e- pair
Found in RBC
Why is Carbon monoxide poisoning toxic? Transition Metals?
The CO replaces O2 with a more stable bond preventing oxyhemoglobin forming and requires a high O2 saturation to reverse.
What is Chelation?
Replacing simple ligands with multi dentate ligands like EDTA
Used for pt. with metal poisoning to remove the metal.
A chelate is more stable than unidentate ligands
What is EDTA?
Ethylenediamine tetra acetic acid
Donates 6 lone pairs
Why does the Chelate effect work?
Including EDTA example
2 reactions may have the same enthalpy but different entropy (amount of species)
EDTA bonds, allowing more species to be removed from ligand so increases entropy.
To reverse an entropic increase requires a lot of energy so is difficult to revers
[Cu(H2O)6] + EDTA →
[Cu(EDTA)] + 6H2O
We go from 2 species to 7
What do coloured compounds depend on?
Transition element
Oxidation state
Ligands
Co-ordination number
How do coloured compounds form?
The e- in the partially filled d orbital is excited to a higher energy, absorbing energy
The energy that isn’t absorbed is shown as a colour reflected.
Colour Compound Equation
Energy Difference=
wavelength
∆H = (hc)/ λ
What is the importance of coloured transition metals?
We can use colorimetry to find the concentration
What are heterogenous catalysts?
Different phase to reactants
Increase SA
Spread on support medium Easily poisoned and efficiency reduced
What is the Haber Process Catalyst
N2 + 3H2 ⇌ 2NH3
Iron Catalyst (Heterogenous)
Pea sized lumps to incr. SA
Poisoned in 5 years by gases
What is the Contact Process Catalyst?
2SO2 + O2 ⇌ 2SO3 V2O5 catalyst (Heterogenous)
SO2+ V2O5 → SO3 + V2O5
2V2O5 + O2 → 2V2O5
What is homogenous catalyst?
The same state as the reactants
What is the Iodine Process catalyst?
Iron Catalyst (Homogenous) S2O8-² +2I- → 2SO4-² + I2
The two negative ions would repel so catalyst provides an alternate route
What is autocatalysis?
One of the products acts as a catalyst
