Transition metals

• Transition element


  elements with an incomplete d-subshell that can form at least one stable ion with an incomplete sub shell
• Electron configuration of chromium

  [Ar] 4s1 3d5
• Electron configuration of copper

  [Ar] 4s1 3d10
• Why do chromium and copper have different electron configurations than the pattern

  As half full and full d-subshells are energetically more stable
• Properties of transition elements

  -Variable oxidation states-Form complex ions-Form coloured compounds-Behave as catalysts
• Complex ion


  A transition metal ion bonded to one or more ligands by coordinate bonds
• How can transition elements act as catalysts?


  They can change oxidation states by gaining or losing electrons within their d orbitals. This means they can transfer electrons to speed up reactions. They are good at adsorbing substances onto their surfaces to lower the activation energy.
• Co-ordination number


  The number of co-ordinate bonds formed to a central metal ion
• Monodentate ligand


  Can form one dative covalent bond to the central metal ion
• Bidentate ligand


  Can form two dative covalent bonds to the central metal ion as it containing 2 atoms with lone pairs of electrons
• Octahedral complexes


  • 6 coordinate bonds, 90 bond angles
• Tetrahedral complexes


  • 4 coordinate bonds, 109.5° bond angles
• Square planar complexes


  • 4 coordinate bonds, 90° bond angles, only for Ni, Pd and Pt
• Optical isomer


  Non-superimposable mirror images
• Complex ions with optical isomerism

  • Octahedral complexes with bidentate ligands
• How cis-platin acts as an anti-cancer drug

  Binds to cystine and guanine which distorts the shape of DNA and prevents DNA replication so mitosis can't occur
• Adverse effects of cis-platin as a cancer drug

  Binds to healthy cells so can cause side-effects such as hair loss
• Ligand substitution


  When one ligand in a complex is replaced by another
• Ligand substitution makes complexes more stable than the original
• Ligand substitution does not change the coordination number and geometry if the ligands are a similar size, if there is a large difference in size like water and chlorine, the coordination number and geometry will change
• Transition element ion in solution

  Is a hexaaqua complex ion
• Why does the coordination number and geometry change in the reaction from hexaaqua copper(II) to [CuCl4]2-?


  As chloride ions are larger that water molecules so only 4 are able to bond to the central metal ion, geometry changes from octahedral to tetrahedral
• Number of OH- substituted is the same as the charge on the initial ion