Atomic Emission Spectra

Atomic emission spectra provide evidence that electrons are arranged in energy levels. An energy level is the discrete (fixed) amount of energy that an electron possesses. A continuous spectrum of colours are seen when white light passes through a prism. We can see the actual colours because their corresponding frequencies are found in the visible section of the electromagnetic spectrum. 

When energy is supplied to individual elements they emit a spectrum containing emissions of a particular wavelength. This is called a line spectrum. The following process occurs:

  1. Electrons gain energy and move from their lowest available energy level (ground state) to a higher available energy level (excited state).
  2. Electrons themselves occupy a fixed energy level, and so have a fixed quantum of energy.
  3. As the electron drops back down to lower available energy level, a fixed amount of energy is emitted as a photon of light, which shows as a line in the emission spectrum.
  4. When the electrons drop to the second energy level, that frequency of light is emitted in the visible section. This is called the Balmer series.

E2- E1= hf

where E2-E1 is the difference in energy between the excited state and energy level n =2

h = Plank’s constant

f = frequency of light 

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