Question

What is the principle of flame emission spectroscopy?

Answer 1

Hint : Flame emission spectroscopy is one of the branches of atomic absorption spectroscopy. It is also known as Flame photometry. Currently, it has become a necessary tool in the field of analytical chemistry. Flame photometers can be used to determine the concentration of certain metal ions like sodium, potassium, calcium etc.

Complete Step By Step Answer:
Sample is sprayed into a flame and it is converted to droplets. Due to the thermal energy of the flame the solvent in the droplets evaporate, leaving behind fine residue, which are converted to neutral atoms,
These neutral atoms get energy from thermal energy and go to excited states but they are unstable at excited states, so they return to ground state with emission of specific wavelength radiation.
Principle- The wavelength of the radiation emitted is characteristic of the elements and is used to identify the elements (Qualitative Analysis). The intensity of the radiation emitted depends upon the concentration of the element analyzed (Quantitative Analysis).
The wavelength of the radiation emitted is given by the following equation –
$\lambda =hc/{{E}_{2}}-{{E}_{1}}$
where $h$ = Planck's constant, $c$ = Velocity of light, ${{E}_{2}}-{{E}_{1}}$ = energy levels of excited and ground state respectively.

Note :
Flame emission spectroscopy is useful for the determination of alkali and alkaline earth metals. It is used in the determination of lead in petrol and determination of calcium and magnesium in cement.