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