Spectral analysis is primarily designated analysis and quantitative analysis; when analysis, you must understand the atomic structure and atomic electronic properties. Experimental results show that, the atom of any element contains a small structure close to the atomic nucleus, the nucleus consists of protons and neutrons, nuclear distribution of electronic, each electron with a negative charge, the charge and size of proton was equal, but opposite sign. Neutrons are uncharged, in a neutral atom, proton and electron number equal to the number; this number represents each element’s characteristic, commonly referred to as the atomic number.
Due to the distribution of electrons which surrounded the nucleus is not arbitrary, but have certain laws, so it shows different chemical properties and different spectrum of each elements, thus we can imagine that in a certain electronic track, while the electron in each track (or state) with the energy not identical, each track can be regard as a level of the equivalent of atoms. It is relatively simple and straightforward for Bohr atom model diagram to explain the electronic structure of the atomic nucleus outside.
In fact, electronic has fluctuation, this nature make the electrons orbit concept of atoms lost its meaning, quantum mechanical electronic state also know as wave function replaced this concept and can reflect the image of the atoms , the surrounding of the nucleus space electronic is surrounded according to the probability distribution, the probability distribution is called the ” electronic cloud”，the calculation of the electron cloud density was on the basis of the theory of quantum mechanics and is coincided with the first track of wave ear hydrogen atom.