AQA A Level Chemistry
- Paper 3
what colour is {Fe(H2O)6}2+ - ANSWER pale green
Transition Metal definition - ANSWER D block elements that form at least one stable
ion with a partially filled d orbital
Classic elements which are not transition metals despite being D-Block elements -
ANSWER Scandium and Zinc
properties of transition metals which are NOT shared by other metals - ANSWER -
multiple oxidation states
-coloured ions in solution
-great catalysts
-form complexes with ligands
ligand - ANSWER a molecule which forms a dative bond with a transition metal
complex ion - ANSWER A transition metal ion bonded to one or more ligands by
coordinate bonds
co-ordination number - ANSWER The number of co-ordinate bonds formed to a central
metal ion
What is an example of incomplete ligand substitution? - ANSWER [Cu(NH3)6]2+ to
[Cu(NH3)4(H2O)2]2+
why does the coordination number not change when substituting water for ammonia ? -
ANSWER because they are of a similar size
Why does incomplete ligand substitution usually occur? - ANSWER when substituting
ligands of a different size
, Denticity - ANSWER the number of dative bonds that can be formed with a transition
metal by one ligand
bidentate - ANSWER When a ligand can form two co-ordinate bonds in a complex ion.
monodentate (or unidentate) - ANSWER A ligand that can form one bond
Multidentate - ANSWER A ligand that can form multiple bonds
Chelate effect - ANSWER the ability of multidentate ligands to form more stable metal
complexes than those formed by similar monodentate ligands
Why is the chelate effect a largely entropic effect? - ANSWER As you the number of
moles of molecules in the products of the reaction increase. This leads to a large
increase in entropy and this brings the Gibbs free energy below zero for the change.
Why is enthalpy change negligible in ligand substitution? - ANSWER The (dative)
bonds being broken and made are the same strength, amount and type.
Why is carbon monoxide toxic? - ANSWER CO can from a strong dative bond with
haemoglobin. This is a stronger bond than that made with oxygen and so it replaces the
oxygen attaching to the haemoglobin. This can starve the body of oxygen.
Ligand exchange/substitution - ANSWER when one ligand in a complex ion is replaced
by a different ligand
What are the four main geometries for complex ions? - ANSWER Octahedral,
Tetrahedral, Square planar, Linear
What ligands tend to form octahedral complexes? - ANSWER water and ammonia
What ligands tend to form tetrahedral complexes? - ANSWER Chloride
What ligands tend to form square planar complexes? - ANSWER Nickel, Palladium,
Platinum
What ligands tend to form linear complexes? - ANSWER Copper, silver and gold
What type of isomerism can square planar complexes exhibit? - ANSWER cis-trans
isomerism
What does cisplatin look like? - ANSWER
What does transplatin look like? - ANSWER
- Paper 3
what colour is {Fe(H2O)6}2+ - ANSWER pale green
Transition Metal definition - ANSWER D block elements that form at least one stable
ion with a partially filled d orbital
Classic elements which are not transition metals despite being D-Block elements -
ANSWER Scandium and Zinc
properties of transition metals which are NOT shared by other metals - ANSWER -
multiple oxidation states
-coloured ions in solution
-great catalysts
-form complexes with ligands
ligand - ANSWER a molecule which forms a dative bond with a transition metal
complex ion - ANSWER A transition metal ion bonded to one or more ligands by
coordinate bonds
co-ordination number - ANSWER The number of co-ordinate bonds formed to a central
metal ion
What is an example of incomplete ligand substitution? - ANSWER [Cu(NH3)6]2+ to
[Cu(NH3)4(H2O)2]2+
why does the coordination number not change when substituting water for ammonia ? -
ANSWER because they are of a similar size
Why does incomplete ligand substitution usually occur? - ANSWER when substituting
ligands of a different size
, Denticity - ANSWER the number of dative bonds that can be formed with a transition
metal by one ligand
bidentate - ANSWER When a ligand can form two co-ordinate bonds in a complex ion.
monodentate (or unidentate) - ANSWER A ligand that can form one bond
Multidentate - ANSWER A ligand that can form multiple bonds
Chelate effect - ANSWER the ability of multidentate ligands to form more stable metal
complexes than those formed by similar monodentate ligands
Why is the chelate effect a largely entropic effect? - ANSWER As you the number of
moles of molecules in the products of the reaction increase. This leads to a large
increase in entropy and this brings the Gibbs free energy below zero for the change.
Why is enthalpy change negligible in ligand substitution? - ANSWER The (dative)
bonds being broken and made are the same strength, amount and type.
Why is carbon monoxide toxic? - ANSWER CO can from a strong dative bond with
haemoglobin. This is a stronger bond than that made with oxygen and so it replaces the
oxygen attaching to the haemoglobin. This can starve the body of oxygen.
Ligand exchange/substitution - ANSWER when one ligand in a complex ion is replaced
by a different ligand
What are the four main geometries for complex ions? - ANSWER Octahedral,
Tetrahedral, Square planar, Linear
What ligands tend to form octahedral complexes? - ANSWER water and ammonia
What ligands tend to form tetrahedral complexes? - ANSWER Chloride
What ligands tend to form square planar complexes? - ANSWER Nickel, Palladium,
Platinum
What ligands tend to form linear complexes? - ANSWER Copper, silver and gold
What type of isomerism can square planar complexes exhibit? - ANSWER cis-trans
isomerism
What does cisplatin look like? - ANSWER
What does transplatin look like? - ANSWER
