F325 - Transition Elements Flashcards
What metals are not transition elements and why?
Scandium and zinc.
They do not have any ions with partially filled d orbitals.
Sc3+ has an empty d orbital.
Zn2+ has a completely full d orbital.
What is a transition element?
A d block element that forms an ion with an incomplete d sub shell.
What sub shells overlap?
4s before 3d.
Also lost before.
What metals do not fill regularly?
Chromium: the 3d and 4s all contain 1 electron with no completely filled.
Copper contains full 3d orbitals but only 1 electron in the 4s orbital.
Describe how metals act as effective catalysts.
Provide a surface on which the reaction can take place.
Reactants are adsorbed onto the surface of the metal and held in place while the reaction occurs.
The products are then designed and the metal is unchanged.
Can change oxidation states by losing or gaining electrons, they can bind to reactants forming intermediates as part if a chemical pathway with a lower activation energy.
Describe the Haber process.
N2 + 3H2 —> 2NH3 all (g)
Makes ammonia.
Iron catalyst increases rate and lowers temp for reaction.
Ammonia used in manufacturing fertilisers.
Describe the contact process.
Sulphur dioxide -> sulphur trioxide in the manufacturing of sulphuric acid (H2SO4).
2SO2 + O2 —> 2SO3
Vanadium (V) oxide. V2O5
Production of fertilisers.
Describe the hydrogenation if alkenes.
C2H4 + H2 —> C2H6
Nickel catalyst lowers temp and pressure.
Hydrogenation if unsaturated veg oils.
Describe the decomposition of hydrogen peroxide.
2H2O2 (aq) —> 2H2O + O2
Manganese (IV) oxide. MnO2.
Preparation of oxygen gas.
Describe the reaction of metals with NaOH
Cu2+
Co2+
Fe2+
Fe3+
Cu2+ : pale blue solution -> pale blue precipitate.
Co2+ : pink solution -> blue precipitate. Beige in air.
Fe2+ : pale green -> green precipitate. Turns rusty brown at surface standing in air.
Fe3+ : pale yellow -> rusty brown.
Metal2+ + 2OH —> metal(OH)2
3 3 OH3
What is a complex ion?
A transition metal bonded to one or more Ligands by co ordinate bonds (dative covalent bond)
What is a ligand?
A molecule or ion that can donate a pair of electrons with the transition metal ion to form a co ordinate bond.
What is a co ordinate bond?
A bond in which one of the bonded atoms provides both electrons for the shared pair.
Dative for transition metals.
What Is a monodentate ligand?
The Logan donates only one pair of electrons to the central metal ion to form one co ordinate bond.
What is the most common shape of complex ions?
Octahedral with 6 co ordinate bonds.
All bond angles are 90 degrees.
What are stereoisomers?
Species with the same structural formula but with a different arrangement if the atoms in space.
what is cis/trans isomerism?
Cis: the two Cl- Ligands are adjacent on a corner, at 90 degrees from each other.
Trans: two Cl- Ligands are opposite, at 180 degrees from each other.
What is a bidentate ligand?
It can donate two lone pairs to the central metal ion to form two co ordinate bonds.
What is optical isomerism?
Non superimposable mirror images.
Mirror image flip.
What is ligand substitution?
A reaction in which one ligand in a complex ion is replaced by another ligand.
Describe the reaction of aqueous copper ions and ammonia.
Pale blue aqueous copper ions.
When excess aqueous ammonia is adde it forms a deep blue solution.
4 of the water Ligands are replaced by four ammonia Ligands.
[Cu(H2O)6]2+ + 4NH3 ><
[Cu(NH3)4(H2O)2]2+ + 4H2O
If only a small amount of ammonia is added Cu(OH)2 forms, which forms a pale blue precipitate.
Describe the reaction of copper (II) ions and hydrochloric acid.
The aqueous solution containing copper (II) ions is a pale blue solution, when HCL is added it turns to a green solution, then to yellow.
[Cu(H2O)6]2+ + 4Cl- <>
[CuCl4]2- + 6H2O
Chlorine Ligands are larger than water Ligands and have stronger repulsions. This forms a tetrahedral shape with 4 Ligands.
Describe the reaction of cobalt (II) ions and conc hydrochloric acid.
An aqueous solution of colbalt (II) ions has a pale pink colour. When conc HCL is added the solution changes to dark blue.
[Co(H2O)6]2+ + 4Cl- ><
[CoCl4]2- + 6H2O
The six water molecules in the complex ion are replaced by four chlorine ions.
Why is carbon monoxide and haemoglobin an example of ligand substitution?
Describe haemoglobin.
Carbon monoxide binds more strongly to haemoglobin than oxygen. If both are present CO will bind and replace if O2 is already present.
Irreversible.
Fe2+ haem group forms a co ordinate bond to oxygen.
What is the stability constant?
Kstab
The equilibrium constant for an equilibrium existing between a transition metal ion surrounded by water Ligands and the complex formed when the same ion has undergone a ligand substitution.
Why Is H2O ignored when calculating Kstab?
All the species are dissolved in water Which is in large excess.
It’s concentration is virtually constant.
What does a high Kstab indicate?
It is more stable than those with lower constants.
The position of eq lies to the right.
What is the equation for MnO4- + Fe2+?
MnO4- + 8H+ + Fe2+ —> Mn2+ + 5Fe3+ + 4H2O.
Fe2+ —> Fe3+ + e-
MnO4- + 8H+ + 5e- —> Mn2+ + 4H2O
What is the equation for iodine and thiosulphate?
2S2O3 2- + I2 —> 2I- + S4O6 2-
