CHEMISTRY 7405 PAPER 3 STUDY GUIDE 2026
COMPLETE QUESTIONS AND ANSWERS
◉ 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
COMPLETE QUESTIONS AND ANSWERS
◉ 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
