Answer:
Within atoms and molecules electrons can only have certain values for their energy:
We say that energy levels are discretized. We can easily observe the differences between some of these levels by analyzing the light emitted by electrons when moving from one level to another less energetic. The emitted photons have exactly the energy difference between the levels, and as we know that the energy of a photon is:
E = hc / λ
where h is Planck's constant, c is the speed of light and λ is the wavelength.
Explanation:
Each atom is capable of emitting or absorbing electromagnetic radiation, although only at some frequencies that are characteristic of each of the different chemical elements.
If, through the supply of heat energy, a certain element is stimulated in its gas phase, its atoms emit radiation at certain frequencies of the visible, which constitute its emission spectrum.
Thus, the so-called Kirchoff's Law is fulfilled, which indicates that every element absorbs radiation in the same wavelengths in which it emits it. The absorption and emission spectra thus turn out to be the negative one of the other.
Since the spectrum, both emission and absorption, is characteristic of each element, it serves to identify each of the elements of the periodic table, by simple visualization and analysis of the position of the absorption or emission lines in its spectrum.
These characteristics are manifested whether it is a pure element or combined with other elements, so a fairly reliable identification procedure is obtained.
