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:
- Electrons gain energy and move from their lowest available energy level (ground state) to a higher available energy level (excited state).
- Electrons themselves occupy a fixed energy level, and so have a fixed quantum of energy.
- 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.
- 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