An information approach to the description of atoms by introducing
»differential« entropy characteristics of chemical elements
has been developed. These quantities clearly reflect the horizontal
and vertical structure of the periodic table, and the main features
of atomic electron structures, such as delay in filling d- and f-subshells,
the action of Hund\u27s first rule, the anomalies in the electronic
structure of some atoms, the appearance of the first electron having
a given value of some quantum number, etc. The necessity of change
in the position of lanthanides and actinides in the periodic table is
discussed
