CHEM 132, Chapter 20

• Transition metals


  • Similarities within a given period
  • Similarities within a given vertical group
  • Chemistry not affected as greatly by gradual change in number of electrons
• Energy of 3d orbitals in transition metal ions

  Significantly less than that of 4s orbitals
• The first row transition metal ions do not have 4s electrons
• Maximum possible oxidation state for first 5 transition metals


  • Loss of all 4s and 3d electrons
• Maximum oxidation states for last 5 transition metals

  • 2+ ions more common than 3+
• Going from left to right for 4d and 5d transition metals


  General but small decrease in size
• Transition from 3d to 4d metals

  Significant increase in radius
• 4d and 5d transition metals are similar in size
• Complex ion


  Transition metal ion surrounded by a number of ligands
• Coordination compound


  Compound that contains a complex ion
• Counterion


  Anion or cation needed to produce a compound with no net charge
• Coordination number


  • Number of bonds formed between metal ion and ligand
  • Either 2, 4, or 6
• Ligand


  Neutral molecule or ion with lone electron pair that can be used to form a bond with a metal ion
• Ligands


  • Monodentate - forms one bond
  • Bidentate - forms two bonds
  • Polydentate - forms more than two bonds
• Most compounds of complex ions are colored because transition metal ions in complex can absorb visible light of specific wavelengths
• Types of structural isomerism

  • Coordination isomerism - composition of complex ion varies
  • Linkage isomerism - composition of complex ion is same but point of attachment of at least one ligand differs
• Stereoisomers


  Have the same bonds but different spatial arrangements of atoms
• Geometrical isomerism


  • Occurs when atoms or groups of atoms can assume different positions around a rigid ring or bond
  • In octahedral or square planar structures, one ligand must have a pair
  • Cis - same side, trans - opposite sides
  • Octahedrals can also have isomerism based on a triplet - fac (same ligand on one side), mer (same ligand along axis)
• Optical isomerism


  Isomers have opposite effects on plane polarized light
• Chiral


  Objects with superimposable mirror images
• Enantiomers


  Isomers of chiral molecules