The article discusses a new approach to the formation of periods of the Periodic Table of Mendeleev. With the help of the new formula and the first proposed quantum states of the outer electron shells of atoms of chemical elements, the periods of the periodic table are reformatted. It is supposed to reduce the number of periods in the table by introducing the corresponding sub-periods. This is confirmed by the material given in the article. The following description of the order of formation of electron layers is proposed: the principal quantum number (n), then the newly proposed quantum states of electrons («first» and «second»), which in turn constitute the electronic configurations of sub-periods in periods, and only then the remaining quantum orbitals (s, p, d and f).