ENERGY VARIATIONS OF 4s-3d ORBITALS AND EXCEPTIONS IN ELECTRON CONFIGURATIONS OF Cl AND Fe ELEMENTS

This article analyzes the variability of the energy levels of 4s and 3d orbitals, as well as the peculiarities of electron filling sequences in the elements Cl and Fe. It is shown that the various valence states of Cl (1, 3, 5, and 7) and Fe (2, 3, and 6) depend on the electron configuration and orbital energies. Furthermore, it is noted that the classical interpretation of Klechkovskiy’s rule does not always apply to real atomic systems, as electrons are distributed between outer and inner shells depending on their interactions and energy balance. The examples of Cl and Fe demonstrate that the complex distribution of electrons between outer and inner shells creates difficulties for students and in teaching theoretical chemistry.