Topic 28
Chemistry of
Transition
Elements

define a transition element as a d-block element which forms one or more stable ions with incomplete d orbitals

sketch the shape of a 3dxy orbital

sketch the shape of a 3dz2 orbital

understand that transition elements have variable oxidation states

understand that transition elements behave as catalysts

understand that transition elements form complex ions

understand that transition elements form coloured compounds

explain why transition elements have variable oxidation states in terms of the similarity in energy of the 3d and the 4s sub-shells

explain why transition elements behave as catalysts in terms of having more than one stable oxidation state

explain why transition elements behave as catalysts in terms of vacant d orbitals that are energetically accessible and can form dative bonds with ligands

explain why transition elements form complex ions in terms of vacant d orbitals that are energetically accessible

describe and explain the reactions of transition elements with ligands to form complexes

describe and explain the complexes of copper(II) ions with water and ammonia molecules and hydroxide and chloride ions

describe and explain the complexes of cobalt(II) ions with water and ammonia molecules and hydroxide and chloride ions

define the term ligand as a species that contains a lone pair of electrons that forms a dative covalent bond to a central metal atom/ion

understand and use the term monodentate ligand including as an example H2O

understand and use the term monodentate ligand including as an example NH3

understand and use the term monodentate ligand including as an example Cl–

understand and use the term monodentate ligand including as an example CN–

understand and use the term bidentate ligand including as an example 1,2-diaminoethane, en, H2NCH2CH2NH2

understand and use the term bidentate ligand including as an example the ethanedioate ion, C2O42–

understand and use the term polydentate ligand including as an example EDTA4–

define the term complex as a molecule or ion formed by a central metal atom/ion surrounded by one or more ligands

describe the geometry (shape and bond angles) of transition element complexes which are linear

describe the geometry (shape and bond angles) of transition element complexes which are square planar

describe the geometry (shape and bond angles) of transition element complexes which are tetrahedral

describe the geometry (shape and bond angles) of transition element complexes which are octahedral

state what is meant by coordination number

predict the formula and charge of a complex ion, given the metal ion, its charge or oxidation state, the ligand and its coordination number or geometry

explain qualitatively that ligand exchange can occur, including the complexes of copper(II) ions with water and ammonia molecules and hydroxide and chloride ions

explain qualitatively that ligand exchange can occur, including the complexes of cobalt(II) ions with water and ammonia molecules and hydroxide and chloride ions

predict, using E⦵ values, the feasibility of redox reactions involving transition elements and their ions

describe the reactions of MnO4–/C2O42– in acid solution

perform calculations involving MnO4–/C2O42– in acid solution given suitable data

describe the reactions of MnO4–/Fe2+ in acid solution

perform calculations involving MnO4–/Fe2+ in acid solution given suitable data

describe the reactions of Cu2+/I–

perform calculations involving Cu2+/I– given suitable data

perform calculations involving other redox systems given suitable data

define and use the term degenerate d orbitals

define and use the term non-degenerate d orbitals

describe the splitting of degenerate d orbitals into two non-degenerate sets of d orbitals of higher energy, and use of ΔE, in octahedral complexes, two higher and three lower d orbitals

describe the splitting of degenerate d orbitals into two non-degenerate sets of d orbitals of higher energy, and use of ΔE, in tetrahedral complexes, three higher and two lower d orbitals

explain why transition elements form coloured compounds in terms of the frequency of light absorbed as an electron is promoted between two non-degenerate d orbitals

describe, in qualitative terms, the effects of different ligands on ΔE, frequency of light absorbed, and hence the complementary colour that is observed

use the complexes of copper(II) ions with water and ammonia molecules and hydroxide and chloride ions as examples of ligand exchange affecting the colour observed

use the complexes of cobalt(II) ions with water and ammonia molecules and hydroxide and chloride ions as examples of ligand exchange affecting the colour observed

describe geometrical (cis/trans) isomerism shown by complexes, e.g. square planar such as [Pt(NH3)2Cl2]

describe geometrical (cis/trans) isomerism shown by complexes, including those associated with bidentate ligands, e.g. octahedral such as [Co(NH3)4(H2O)2]2+ and [Ni(H2NCH2CH2NH2)2(H2O)2]2+

describe optical isomerism shown by complexes, including those associated with bidentate ligands, e.g. [Ni(H2NCH2CH2NH2)3]2+ and [Ni(H2NCH2CH2NH2)2(H2O)2]2+

deduce the overall polarity of complexes such as those described in 28.4.1(a) and 28.4.1(b)

define the stability constant, Kstab, of a complex as the equilibrium constant for the formation of the complex ion in a solvent (from its constituent ions or molecules)

write an expression for a Kstab of a complex ([H2O] should not be included)

use Kstab expressions to perform calculations

describe and explain ligand exchanges in terms of Kstab values

understand that a large Kstab is due to the formation of a stable complex ion