What are complexes?
A central metal atom or ion surrounded by a number of negatively charge ions possesing a lone pair of electrons
What are ligands?
Molecules or anions which attach themselves to the central TM ion by using a lone pair of electrons
They form a dative covalent bond or coordinate bond
What is meant by a monodentate,bidentate or hexadentate?
This signifies the number of covalent bonds formed by a ligand
Monodentate=One covalent bond Bidentate=Two covalent bonds Hexadentate=Six covalent bonds
What are the four rules used to name complex ions?
- Number of ligands e.g. mono-,di- amd tetra-
- Identify the ligands e.g ending -o for anions H2O is aqua and NH3 is amine
- Name the central ion e.g copper
- Indicate the oxidation state e.g copper (II)
What are the colour of copper(II), iron(II) and iron(III) solutions?
Copper(II)=Blue solution
Iron(II)=Green solution
Iron(III)=Brown solution
What is the formula of the precipitate formed when copper(II) reacts with sodium hydroxide and ammonia solution?
Include the co-products
- Sodium hydroxide=Cu(OH)2 (s) and H20
- Ammonia solution=Cu(OH)2 or Cu(NH3)4
Define coordination number
The number of bonds from the central ions to ligands
What are the ligands in hexaquacopper (II) and describe why it was given its name?
- Hex- because it has six ligands
- -Aqua- because all of its ligands are water
- Copper because the central ion is a copper ion
- Copper (II) because the oxidation state of copper is +2
How do you calculate the overall charge of a complex ion?
The sum of the charge on the central ion and the charges of the ligands
Describe why not all d-block elements are transition metals
Transition metals have a partially full d sub-shell this means at least 3d1 and below 3d10
What is the filling and emptying order of electrons sub shells?
Filling=1s 2s 2p 3s 3p 4s 3d
Emptying=4s 3d 3p 3s 2p 2s 1s
What are the five features of a transition metal?
- Colourful compounds
- Used as catalysts
- Multiple ions with various oxidation states
- Form complexes
- Ion of element has partially filished d subshell
Why is zinc not a transition metal?
Zinc ion has a full d sub shell
What is hetergeneous and homogeneous catalysis?
- Hetergenous=The catalyst is in a different state to the reactants
- Homogeneous=The catalyst is in the same state as the reactants
How does heterogenous catalysis involving a TM occur?
TM use electrons of atoms on the metal surface to form weak bonds to reactants
Once the reaction is over these bonds are broken
How does homogeneous catalysis involving a TM occur?
TM ion forms an intermediate compound with one or more of the reactants
This is then broken down to form the products
Why are TM effective catalysts in redox reactions?
They can readily move from one oxidation state to another
What is formed when Copper(II) reacts with:
* sodium hydroxide
* ammonia solution
- Blue ppt
- Dark blue solution
What is formed when Iron(II) reacts with sodium hydroxide?
Iron(II) is a green solution
A dirty/dark green ppt
What is formed when iron(III) reacts with sodium hydroxide?
Iron(III) is an orange solution
Brown/orange ppt
What happens when d block compound absorbs light?
- Light is only absorbed if the energy matches the energy gap between energy levels in atom
- One electron becomes excited and is promoted to a higher energy level
- The frequency of light absorbed is dependent on the energy gap
The colour seens corresponds to the transmitted light which is not absorbed
What can affect the colour of a TM?
- Number of d-electrons in TM ion
- Arrangement of ligands around the ion~affects the splitting of the d sub-shell
- Nature of the ligands
What is ligand substitution?
Reactions occur when one ligand displaces another
Ligand substitution occurs if the new complex formed is more stable than the previous complex
What happens to the ion with the more positive electrode potential in a redox reaction?
- Donates electrons
- It is oxidised
- It is the reducing reagent
