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• Physical methods for characterizing inorganic compounds

  • Melting/Boiling Points
  • Mass Spectroscopy
  • Other Physical Properties
• Melting/Boiling Points

  • Inorganic compounds are often ionic, and so have very high melting points
  • Melting and boiling points are not useful in identifying an inorganic compound, but they can be used to assess its purity, if they are accessible
• Mass Spectroscopy


  • Used to determine the molar mass of compounds
  • When combined with elemental analysis, can determine the chemical formula of the substance
  • Analysis of fragmentation pattern can be used to gain structural information, but this is not usually done due to complex fragmentation patterns
• Taste and smell are no longer recommended for characterizing compounds due to potential toxicity
• "Crunchiness"


  A useful physical property that can be used to distinguish between ionic and non-ionic compounds
• Spectroscopic/Structural Methods


  • UV-Vis Absorption Spectroscopy
  • IR Absorption Spectroscopy
• UV-Vis Absorption Spectroscopy

  Can be used to determine the general type of atom bound to a metal and the geometry about the metal
• Common Chromophores


  • Alkene
  • Alkyne
  • Carbonyl
  • Carboxyl
  • Amido
  • Azo
  • Nitro
  • Nitroso
  • Nitrate
• IR Absorption Spectroscopy


  • Can be used to fingerprint a compound
  • In simple compounds, the number, energy and intensity of the IR transitions are directly related to the geometry of the compound and which atoms are bound to which other atoms
  • For complex compounds, IR becomes more difficult to interpret
  • Useful to determine the presence of complex counter ions like PF6, ClO4, BF4 due to their distinctive absorptions
• IR Absorptions of Common Functional Groups

  • Alkane (C-H)
  • Alcohol (O-H)
  • Alkene (C=C, C=C-H)
  • Alkyne (C≡C, C≡C-H)
  • Nitrile (C≡N)
  • Aromatics
  • Amines (N-H)
  • Carbonyls (C=O, CHO, RCOR, RCOOR, RCOOH)