5.3 Flashcards
What are the electron configurations of transition metal ions?
When forming ions, work out the electron arrangement of the atom then remove electrons from the 4s first (a transition metal ion will not have any electrons in the 4s sub-shell)
The highest possible oxidation state of a transition metal is the number of electrons in the 4s and 3d subshells.
What are transition metals?
d-block elements that have an ion with an
incomplete d-sub-shell.
What are ligands?
A ligand is an atom, ion or molecule with a lone pair of electrons that can be donated to a transition metal ion forming a coordinate bonds.
monodentate: H2O, Cl – and NH3
bidentate: NH2CH2CH2NH2 (‘en’)
What is a complex ion?
A central transition metal ion bonded to at least 1 ligand by coordinate bonds.
What is the coordination number?
The total number of coordinate bonds in a complex ion.
What shape would a six-fold coordination be?
Octahedral
What shape would a four-fold coordination be?
Tetrahedral or square planar (usually seen with Ni, Pd and Pt)
Examples of cis-trans isomerism?
[Pt(NH3)2Cl2], [Co(NH3)4Cl2] and [Ni(H2NCH2CH2NH2)2Cl2]
when the angle between the Cl atoms are 90° it shows cis isomerism, and when the angle is 180° it shows trans isomerism.
What is optical isomerism?
Optical isomers are non superimposable mirror images, they rotate plane polarised light by equal amounts but in opposite directions.
[Ni(NH2CH2CH2NH2)3]2+, [Ni(H2NCH2CH2NH2)2Cl2]
What drug is used to help cure cancer?
Cis-platin, it binds to DNA in cancer and prevents cell division.
Chemo can reach and kill cancer cells growing in different parts of the body. Chemo can also therefore kill healthy cells, it can also alter your brain chemistry leading the changes in memory, concentration, fatigue…
What is the biochemical importance of iron?
Haemoglobin contains the haem groups which have an Fe2+ ion at their centre. O2 acts as a ligand and binds reversibly to the Fe2+ ion. The O2 is carried to the cell where it is released.
CO can bind to the same position but stronger and irreversible, reducing the blood’s ability to transport O2 around the body, starving the tissues of O2.
Two examples of the existence of more than one oxidation state for each element in its compounds
Cu2O (+1) and CuSO4 (+2)
K2Cr2O7 (+6) and CrO (+2)
How do transition metals act as catalysts and state two example of the catalytic behaviour of the elements and their compounds and their importance in the manufacture of chemicals by industry
Transition metals provide a surface on which a reaction can take place. Reactants adsorb onto its surface and are held in place whilst the reaction takes place before desorbing and leaving the metal unchanged. Transition metals are good at this because of their ability to change their oxidation states, so they can form intermediates as part of the chemical pathway.
Hydrogenation of unsaturated vegetable oils for the production margarine uses a nickel catalyst so it can be done at lower temperatures and pressures.
The Harper process which produces ammonia for fertilisers: N2 + 3H2 <-> 2NH3
uses an iron catalyst to increase the rate of reaction and lower the temperature at which the reaction takes place.
redox reactions and accompanying colour
changes for:
(i) interconversions between Fe2+ and Fe3+
Under acidic conditions with an oxidising agent like MnO4^- (purple):
Fe^2+ is light green.
Fe^3+ is yellow.
(ii) interconversions between Cr3+ and Cr2O7 2-
Under acidic conditions with a reducing agent like Zn:
Cr^3+ is dark green.
Cr^6+ is orange.
(iii) reduction of Cu2+ to Cu+ and disproportionation of Cu+ to Cu2+ and Cu
Cu2O + H2SO4 -> Cu + CuSO4 + H2O
Cu^2+ is blue.
Cu+ is colourless.
Tests for:
anions: CO32–, SO42–
cations: Cu2+, Fe2+, Fe3+, Mn2+, Cr3+
Precipitation reactions With NaOH solution or ammonia solution, nOH^-: Cu^2+, Fe^2+, Fe^3+, Mn^2+, Cr^3+
Cu(OH)2: pale blue precipitate. (add NH3 -> [Cu(NH3)4(H2O)2]^2+: deep blue]
Fe(OH)2: green (oxidises to Fe(OH)3)
Fe(OH)3: rusty brown
Mn(OH)2: light brown (oxidises to Mn2O3)
Cr(OH)3: grey/ green (add NaOH -> Cr(OH)6^3- (aq): green, add NH3 -> [Cr(NH3)6]^3+: purple)
What are the ligand substitution reaction for copper dissolved in water upon addition of HCl or NH3?
Copper dissolved in water: [Cu(H2O)6]^2+, a blu solution.
When Cl^- is added: [CuCl4]^2-, yellow.
When excess NH3 is added: [Cu(NH3)4(H2O)6]^2+, deep blue.
What are the ligand substitution reaction for when chromium compounds dissolved in water react with NH3?
Chromium dissolved in water: [Cr(H2O)6]^3+, violet solution (green if sulphate ions are present).
When excess NH3 is added: [Cr(NH3)6]^3+, purple.
How many water, chlorine, and ammonia ligands surround a metal ion?
Water: 6
Chlorine: 4
Ammonia: 6
