The properties of the atoms of chemical elements, as well as the composition and properties of the substances they form, are periodically dependent on the charges of atomic nuclei.
Its physical meaning lies in the fact that the properties of atoms of chemical elements are periodically repeated, because the structure of their outer electronic layer is periodically repeated.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.