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75 Cards in this Set
- Front
- Back
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What is a transition element? |
An element with a partially filled d-orbital shell AKA - d-block elements |
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What are base metals? |
Metals that oxidise or corrode easily e.g. Cu, Zn, Fe |
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What are noble metals? |
Opposite of base metals Usually found on the earth in metallic state e.g. Au, Ag, Pd, Ir |
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What are coinage metals? |
Group XI e.g Cu, Ag, Au |
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What is the Aufbau principle? |
Addition of electrons from the lowest energy orbital upwards |
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What is Hund's rule? |
Maximum multiplicity Electrons in degenerate orbitals have the same spins |
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What is the Pauli Exclusion Principle? |
Electrons in the same orbitals have opposite (paired) spins |
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For single metal atoms, what is filled before the 3d orbital? |
4s orbital |
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What gives a single metal atom special stability? |
Half filled + full d-orbital |
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For a metal atom/ ion in a coordinate complex, what is removed before the 3d orbital? |
the 4s orbital |
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What is the orbital notation of Argon? |
1s2 2s2 2p6 3s2 3p6 [Ar] can be used as a shorthand for larger atoms |
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What do compounds in high oxidation states act as? |
Oxidising agents |
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What do compounds with metals in low oxidation states act as? |
Reducing agents |
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How can metals act as catalysts by redox? |
By changing oxidation states during the catalytic process e.g. Suzuki Coupling |
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Why is metal redox essential for some species to live? |
Some bacteria (e.g. Acidithiobacillus ferrooxidans) use redox chemistry as their energy source |
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How do transition metals act as lewis acids? |
Accept electrons Attract lone pairs of electrons from other molecules - ligands - to form a type of covalent bond: coordinative/dative/donor/metal-ligna bond |
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What is a coordination number? |
The number of donor atoms bonded to the metal |
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What are ligands? |
Molecules that donate a lone pair to the metal to form a dative bond (Lewis bases) Can be neutral or negatively charged Different ligands = different bond strength |
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What is meant by monodentate? |
Where a lone pair of electrons is donated from one donor atom |
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What is meant by multidentate? |
Ligands which can donate lone pairs from more than one donor atom |
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What is meant by bidentate? |
Ligands that have two donor atoms |
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What is the chelate effect? |
Where complexes of multidentate ligands have greater stability than those of monodentate ligands This causes multidentate ligands to readily displace monodentate ones |
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What do multidentate ligands do in biology? |
Sequester metals e,g, porphyrins Hemin Tetradentate - a porphyrin that carries oxygen in blood by coordination to the Fe cation |
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What is chelation therapy? |
Chelating ligands find use in water softening, decontamination + detoxification |
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Why is selectivity an issue with EDTA? |
EDTA will remove nutrients from the body |
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How are coordinate complexes named? |
Cation then anion Anionic ligands first, then neutral ligands, then metal (with os) Number of liginds defined by Greek prefix (mono, di, tri, tetra, penta, hexa, hepta, octa) |
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What are some other rules for nomenclature of coordination complexes? |
Ammonia = amine Water = aqua Carbon = carbonyl Anionic ligands end -o - chloro, bromo, nitrato Anionic metals end - ate Some metals take Latin name |
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What are the Latin names of metal that need to be known? |
Iron = ferrate Lead = plumbate Copper = cuprate Silver = argenate Gold = aurate |
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How do we name neutral coordination complexes? |
As one word |
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If the ligands name begins with mono, di, tri, etc. - how do we denote the number of ligands |
bis, tris, tetrakis, pentakis, hexakis, etc. |
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What is extractive metallurgy? |
The purification of metals from their ores - concentration of the metal's value - seperation from unwanted elements in the ore - reduction of the oxidised metals of value -refinement to a purity suitable for use |
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What is pyrometallurgy? |
Use of heat to separate metals from their ores |
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What is roasting? |
Converts ores to metal oxides e.g. 2ZnS(s) + 3O2(g) -> 2ZnO(s) + 2SO2(g) |
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What is smelting? |
Reduces metal oxides to liquid (or gaseous metals, often using C as a reductant e.g. 2MO(s) + C(s) -> 2M(s) + CO2(g) |
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What are the problems with pyrometallurgy? |
Large energy cost (T up to 2000K) |
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How are impurities removed from pyrometallurgy reactions? |
Calcium carbonate + silica (flux) used to remove impurities as slag |
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How is molten metal separated from slag? |
Drawn off as liquids, separated by densities |
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What is hydrometallurgy? |
Uses aqueous chemistry to extract metal from ores, relies heavily on coordination chemistry Metal ions leached from ores into solution using acids, bases, ligands with high affinities or redox chemistry |
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How are metals separated in hydrometallurgy reactions? |
Separated + purified by precipitation or selective extraction as coordination complexes |
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What metals is hydrometallurgy used for? |
Gold Copper Nickle Zinc Uranium |
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What does hydrometallurgy exploit? |
Coordination chemistry to extract metal from rock as a water soluble complex |
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What are the advantages of hydrometallurgy? |
Does not require high temp - less energy + lower emissions than pyrometallurgy Reagents can be recycled - efficient Smaller scale plants are more versatile - no need to transport ore or for massive facilities Can process lower grade ores than pyrometallurgy |
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What is meant by low grade ores? |
Ores with small metal content |
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Why is tetrahedral more common than square planar? |
Favoured electronically + sterically |
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What are coordinative isomerism? |
AKA - Structural Isomerism Isomers which differ in which of the ligands are bonded to the metal and/or which act as counterions |
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What is linkage isomerism? |
Isomers which differ by which donor atom(s) the ligand(s) use to bond to the metals |
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What is stereoisomerism? |
The same ligands are bonded by the same donor atoms to the metal but in different spatial arrangements Many isomers for octahedral complexes Bidentate ligands complicate further |
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blanc |
matt |
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What is the down-side of stereoisomerism? |
Things can get very complicated as the number of ligands increases |
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What is valence bond theory for coordinate covalent bonds? |
For coordinate covalent bonds, both bonding electrons are supplied by the ligand |
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What is valence bond theory for octahedral complexes? |
The valence orbitals are d^2sp^3 hybrids |
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What hybridizations can form d^2sp^3 |
4s, 4p + 3d orbitals: inner orbital complexes (1st row transition metals) 5s, 5p + 4d orbitals: outer orbital complexes (2nd row transition metals) |
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What does valence bond theory explain? |
Paramagnetism |
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What is crystal field theory based om? |
Based on energies of transition metal d-orbitals when interacting with electric field of surrounding ligands Treats ligands as point charges |
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What is crystal field theory? |
In absence of ligands, the d-orbitals are degenerate Interactions with ligands increase their energies |
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What is the energy of d-orbitals in a complex according to crystal field theory? |
Dependent on the coordination geometry of the complex |
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What happens at high-spin configurations? |
Electrons fill eg before pairing t2g |
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What happens at low-spin configurations? |
Electrons pair in t2g before filling eg |
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What does increasing energy gap favour? |
Low-spin configuration |
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When is a complex low-spin? |
If Delta-o is larger than electron pairing energy, complex will be low-spin |
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What is Delta-o dependent on? |
The strength of the ligand field, the spectrochemical series |
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For what d-orbitals are high + low spins possible? |
d4, d5, d6 + d7 |
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What orbital can have magnetic properties? |
d-orbital |
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How is the magnetic moment measured? |
With a Gout Balance to determine if high or low spin |
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What is paramagnetic? |
Complex has unpaired electrons |
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What is diamagnetic? |
Complex has no unpaired electrons |
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What can crystal field stabilisation energy (CFSE) be used for? |
To explain kinetics of reactions Quantify stabilisation of electronic configuration |
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What happens when orbitals in a crystal field have been split? |
Energy must remain constant eg raised + t2g lowered in energy Difference in energy is the CFSE |
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What does adding/removing electrons from high-spin d5 do? |
Increases CFSE Complexes are usually kinetically labile |
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What does adding/removing electrons from low-spin d5 do?
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Decreases CFSE Complexes are usually kinetically inert |
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How does crystal field theory explain colours in transition metal complexes? |
The energy gap between the t2g + eg orbitals is in the visible range of the electromagnetic spectrum Photons of appropriate energy are absorbed, giving colours + promoting d-d transitions d electrons moving from t2g to eg orbitals |
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What is UV/Vis spectroscopy? |
Measure absorption of light Get information on energy gap + the nature of transitions |
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What information do you gain by examining the position, intensity + width of absorption bands? |
Information on environment aroun metal ion |
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What is charge transfer? |
Electron transfer between metal + ligands Evident in Iron heme proteins (Fe2+ / Fe3+) Gives very intense colours No symmetry restrictions |
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What is another transition that can give colour? |
Any transitions require a change in electron spin Much less favourable Only very weak pink colour evident in [Mn(H2O)6]2+ (high spin d6) |
