CHAPTER 25: Transition Elements

CHAPTER 25: Transition Elements

  • Introduction to Transition Elements
  • Oxidation States of Transition   Elements
  • Complex Ions

Learning outcomes:

  • explain what is meant by a transition element, in terms of d-block elements forming one or more stable ions with incomplete d orbitals
  • state the electronic configuration of a first row transition element and of its ions
  • contrast, qualitatively, the melting points and densities of the transition elements with those of calcium as a typical s-block element
  • describe the tendency of transition elements to have variable oxidation states
  • predict from a given electronic configuration, the likely oxidation states of a transition element
  • describe and explain the use of Fe³/Fe², MnO4/Mn² and Cr2O7²/Cr³ as examples of redox systems
  • predict, using E values, the likelihood of redox reactions
  • explain the reactions of transition elements with ligands to form complexes, including the complexes of copper(II) ions with water, hydroxide, ammonia and chloride ions 
  • (i) define the term ligand as a species that contains a lone pair of electrons that forms a dative bond to a central metal atom/ion.
    • define the term complex as a molecule or ion formed by a central metal atom/ion surrounded by one or more ligands
    • describe transition metal complexes as linear, octahedral, tetrahedral or square planar
  • explain qualitatively that ligand exchange may occur, including the complexes of copper(II) ions with water, hydroxide, ammonia and chloride ions
  • describe the shape and symmetry of the d orbitals, and the splitting of degenerate d orbitals into two energy levels in octahedral complexes using the complexes of copper(II) ions with water and ammonia as examples
  • explain the origin of colour in transition element complexes resulting from the absorption of light energy as an electron moves between two non-degenerate d orbitals
  • describe, in qualitative terms, the effects of different ligands on absorption, and hence colour, using the complexes of copper(II) ions with water, hydroxide, ammonia and chloride ions as examples.
  • apply the above ideas of ligands and complexes to other metals, given information