Spectroscopy Atomic emission spectroscopy (AES) Atomic absorption spectroscopy (AAS) UV-visible spectroscopy (UV-Vis) Infrared (IR) spectroscopy Nuclear magnetic resonance (NMR) spectroscopy

What do spectroscopic techniques tell us? Type of atom or molecule (qualitative) Amount of a particular atom or molecule (quantitative) Structure and bonding of a molecule What do spectroscopic techniques utilise? Changes in energy of atoms/molecules in response to electromagnetic radiation

The electromagnetic spectrum Figure 7.1, pg77 The shorter the wavelength, the higher the energy

Exciting electrons Flame test Atomic Emission Spectroscopy (AES) Atomic Absorption Spectroscopy (AAS) Rely on energy change as electrons move from one energy level to another Fig 7.7, page79

Atomic Emission Spectroscopy Calcium Sodium Mercury Cadmium Fig 7.8 and 7.9, page80

Atomic Absorption Spectroscopy (AAS) Fig 7.13, page 83 Can detect over 70 elements Very sensitive (can detect at concentrations of ppm) Quantitative (amount of light absorbed proportional to quantity of substance)

How do you use this information? Fig. 7.14, page 83

UV-visible spectroscopy Fig 7.16, p 86 Absorbance spectrum of chlorophyll Violet (420 nm) Determining absorbance spectrum of substance Determining concentration of a substance Red (660 nm) Fig 7.18, p 87 Absorbance is proportional to concentration. Beer-Lambert Law: A = cl, where A is absorbance and c is the concentration in in molL-1. The remaining values are constant. Green (500 - 520 nm)

How does a UV-vis spectrophotometer work? See Fig 7.15, p86