Introduction

Welcome to the colourful world of…

TRANSITION METALS

transition-metal-compound-solutions-andrew-lambert-photography

 What are Transition Metals?

  • Make up the d-block and f-block (inner transition elements) of the periodic table.
Transition Elements in the Periodic Table
Transition Elements in the Periodic Table
  • Form cations with multiple oxidation states eg. Manganese can exhibit +2, +4, +7 oxidation states, just to name a few.
  • These cations are often the center of many complex ions, known as Coordination Complexes. These species are responsible for the color of gems such as rubies (Cr3+) and sapphires (Fe2+, Fe3+ and Ti4+).

 A More Rigorous Definition

A transition metal is one which forms one or more stable ions which have incompletely filled d orbitals.

Take note that while all transition metals are d-block elements, NOT all d-block elements are transition metals. (By the above definition)

For example,
Zn2+: [Ar]3d10 is NOT a cation of a transition element because the 3d orbitals of Zn are completely filled.
Fe2+: [Ar]3d6 is a cation of a transition element because the 3d orbitals of Fe are incompletely filled.

Coordination Complexes

  • Formed with several molecules or ions (called ligands) surrounding a central metal ion, held by dative covalent bonds (called coordinate bonds)
  • If the coordination complex carries a net charge, the complex is called a Complex Ion.
  • Ligands act as Lewis bases and have at least one lone pair of electrons available for dative bonding.
  • Two types of ligands:
    • Monodentate: Have only one atom capable of binding to a central metal atom or ion eg. H2O, CN–, OH– 
    • Multidentate: Possess lone pairs on different atoms that are separate enough such that both can reach the metal eg. Ethylenediamine
  • A complex ion containing a multidentate ligand is called a chelate.