17A1-2. Transition metals

• Transition metal


  An element that forms one or more stable ions with incompletely filled d-orbitals
• Characteristics of transition metals


  • Hard solids
  • High melting and boiling temperatures
  • Can act as catalysts
  • Form coloured ions and compounds
  • Form ions with different oxidation numbers
  • Form ions with incompletely filled d-orbitals
• Scandium and zinc do not have some of the characteristics of transition metals
• Scandium and zinc form only one ion each and their compounds are not coloured
• Elements in Period 4 of the d-block

  • Scandium
  • Titanium
  • Vanadium
  • Chromium
  • Manganese
  • Iron
  • Cobalt
  • Nickel
  • Copper
  • Zinc
• Abbreviated electronic configuration


  Represents the complete shells with reference to the previous noble gas
• Scandium loses both of its 4s electrons and its only 3d electron, forming the Sc3+ ion
• Zinc loses both of its 4s electrons and none of its 3d electrons, forming the Zn2+ ion
• Scandium and zinc are not classified as transition metals because they form only one ion each and these ions have no incompletely filled d-orbitals
• Common oxidation numbers of transition metals


  • Ti: +3, +4
  • V: +2, +3, +4, +5
  • Cr: +3, +6
  • Mn: +2, +4, +7
  • Fe: +2, +3
  • Co: +2, +3
  • Ni: +2
  • Cu: +1, +2
• The highest common oxidation number increases from Ti (+4) to Mn (+7) as all the 4s and 3d electrons become involved in bonding
• From Fe to Cu, the increasing nuclear charge means that the electrons are attracted more strongly and are less likely to be involved in bonding, so ions with higher oxidation numbers are less common
• Ligand


  A molecule or ion that forms a coordinate covalent bond to a central metal ion in a complex ion
• Dative (coordinate) covalent bonding

  Bonding involved in the formation of complex ions
• Complex ion


  A central metal ion surrounded by ligands
• Coordination number


  The number of ligands bonded to the central metal ion in a complex ion
• The symbol Na+ represents the sodium ion, and Na+(aq) shows that the sodium ion is dissolved in water
• Ligand


  A species that uses a lone pair of electrons to form a dative bond with a metal ion
• Dative (coordinate) bond


  A covalent bond formed between the central metal atom or ion and a ligand, in which both of the bonding electrons are supplied by the ligand
• Complex


  A species containing a metal ion joined to ligands
• Complex ion


  A complex with an overall positive or negative charge
• Coordination number


  The number of dative (coordinate) bonds in the complex
• Methane molecule cannot act as a ligand
• Formation of a transition metal complex ion

  1. Central metal ion

  2. Ligands form dative bonds with metal ion

  3. Overall positive or negative charge on complex ion
• The first product [Cu(H2O)(OH)2]+ is a complex but not a complex ion