What is meant by atomic emission?
Atomic emission means the effect produced when electrons drop from a higher energy level to a lower energy level. When this happens, the electrons will emit the extra energy in the form of electromagnetic radiation. In the case of flame tests, at first the electrons get excited when they are heated and get promoted to the higher energy level ( outer shell). Then the elctron will drop back to lower energy level and in doing so, it will release the excess energy. If copper is used for example, the energy released corresponds to the wavelength of the green colour light and you can see green colour flame produced.
