Transition metals Flashcards
What is a transition metal?
An element that forms at least one stable ion with a partially filled d subshell
What are the two types of catalysts that transition metals can act as?
Transition metals can act as heterogenous catalysts.
Transition metals in solution can act as homogenous catalysts
What are some examples of heterogenous transition metals catalysts?
- Iron in Haber process, iron is solid while N2 and H2 are gases
- Vanadium oxide in the contact process
- Finely divided nickel in hydrogenation reactions
- Platinum in the catalytic oxidation of ammonia
How do heterogenous catalysts work?
Chemisorption.
Reactant molecules are absorbed onto the surface of the molecule,the bonds are weakened and the molecules are help in a more favourable orientation for the reaction
What are some physical properties of transition metals?
- Good conductor of electricity
- Often coloured in aqueous solution
- Many form coloured complexes
- The aqueous metal ions are actually hexaaqua cations
What is a complex?
A central metal atom or ion with ligands bonded by coordinate bonds.
What is a ligand?
An ion or molecule with a lone pair of electrons which forms a coordinate bond with a central metal atom or ion in a complex
How are complexes often written?
on page
What are three neutral ligands?
Aqua - H2O
Ammine - NH3
1,2-diaminoethane (en) -H2NCH2CH2NH2
What are four anion ligands?
Chloro - Cl-
Cyano - CN-
Thiocyano - SCN-
Edta4-
What is a monodentate ligand?
A ligand which uses only one lone pair of electrons to form a coordinate bond with a central metal atom or ion in a complex
What is a bidentate ligand?
A ligand which uses two lone pairs of eletrons to form two coordinate bonds with a central metal atom or ion in a complex
What is a polydentate ligand?
A ligand which uses many lone pairs of electrons to form more than two coordinate bonds with a central metal atom or ion
If a ligand is neutral then what do you do?
If a ligand is neutral, then the charge on the complex is the same as that of the metal ion
What do you do if the ligand is negatively charged
If the ligand is negatively charged then the charge on the ligand is the number on the metal ion + (number of ligands x negative charge)
Why is H2O monodentate?
H2O is monodentate because although it has two lone pairs they cannot separate enough to form separate coordinate bonds
Draw the order of the strength of ligands
The strength depends on the availability of the lone pair of electrons ease of donation
CN-, en, NH3, H2O, OH-, F-, Cl-, Br-, I-
→ decreasing ligand strength
Why does the strenght of the ligand decrease down the halides
The bond is longer therefore weaker
What do alkyl groups do?
They push electrons towards the N atom, destabilising the lone pair, so it is more likely to be donated to the central metal atom or ion in the complex
What is ligand replacement?
A stronger ligand can replace a weaker ligand in a complex
table of chronium
on page
How do you reduce vanadium?
Use zinc in the presence of dilute hydrochloric acid.
How is the +5 oxidation state of zinc achieved
Using an acidified solution of ammonium vanadate (V), NH4VO3. VO3- ionds where V is +5
Write the equations for the reduction of vanadium
on page
How are complexes named?
Based on the number and name of ligands and the mteal ion with the oxidation state e.g.
[Fe(H2O)6]3+ = hexaaquairon (III)
