Inorganic chemistry

• Transition elements


  Elements in the d-block of the periodic table, between groups II and III

  
• Transition elements


  • Have partially filled d-orbitals
  • Can be in their group state or common oxidation state
• Types of transition elements

  • Main transition elements (d-block)
  • Inner transition elements (f-block)
• Filling of d-orbitals in transition elements

  1. 3d elements (Sc to Zn)

  2. 4d elements (Y to Cd)

  3. 5d elements (La to Hg)
• First-row transition series


  • Scandium
  • Titanium
  • Vanadium
  • Chromium
  • Manganese
  • Iron
  • Cobalt
  • Nickel
  • Copper
  • Zinc
• Zinc


  Not a transition element as it has completely filled d-orbitals
• Copper


  Not a transition element as it has completely filled d-orbitals

  
• Chromium and copper have stable electronic configurations with singly or doubly filled d-orbitals

  
• Scandium ion Sc3+ is not a transition element as it has no electrons in the d-orbital
• Physical properties of transition elements

  • High boiling and melting point
  • Hard, dense, and lustrous
  • Good conductors of heat and electricity
  • High densities
• Transition elements


  • Variable oxidation states
  • Form complex ions
  • Form coloured compounds
  • Catalytic activity
  • Paramagnetism
• Transition metals exhibit variable oxidation states due to availability of 4s and 3d electrons for bond formation
• Most transition elements show a common oxidation state of +2 corresponding to removal of 4s2 electrons
• Manganese forms the highest oxidation state of +7
• Complex ion


  Consists of a central metal cation bonded to several anions or molecules (ligands)
• Transition elements form complex ions due to availability of vacant d-orbitals in their ions
• Complex ions can have 4 ligands in tetrahedral arrangement or 6 ligands in octahedral arrangement

  
• Complex ions


  • [Zn(NH3)4]2+
  • [Fe(CN)6]3-

  
• Transition metals with higher oxidation states form more stable complex ions
• Coloured compounds of transition elements

  Due to electronic transitions in partially filled d-orbitals
• Colours of 3d transition metal ions in aqueous solution

  • Sc3+ - Colourless
  • Ti3+ - Purple
  • V3+ - Green
  • Cr3+ - Violet
  • Mn3+ - Violet
  • Mn2+ - Pink
  • Fe3+ - Yellow
  • Fe2+ - Green
  • Co2+ - Pink
  • Ni2+ - Green
  • Cu2+ - Blue
  • Zn2+ - Colourless

  
• Catalytic activity of transition elements

  • Due to low-lying empty d-orbitals available for bond formation
  • Ability to exist in various oxidation states
• Catalytic applications of transition elements

  • Ethane production from ethene using Ni
  • Contact process using V2O5
  • Haber process using Fe
  • Decomposition of chlorate using MnO2

  
• Paramagnetism


  Substances with unpaired electrons, e.g. transition elements with incomplete d-orbitals
• Transition metal atoms/ions without unpaired electrons are diamagnetic
• Examples of paramagnetic transition elements: Cr, Co
• Examples of diamagnetic transition elements: Zn2+, Cu