In the framework of the adiabatic three-particle model of nuclei is given a theoretical description of the stationary states of spherical (deformed) even-even nuclei taking into account the strong nuclear and electromagnetic interactions. In particular, we study the nucleon pairing energy and the energy spectra of two-hole excited states of even-even nuclei in which to fill the outer shell are missed two protons. The efficiency of the model is illustrated by numerical calculations for even-even argon and ferrum isotopes. Key words: adiabatic three-particle model, Schrodinger’s equation, angular and radial correlations of nucleons, even-even nuclei, pairing energy.