The state of a typical Jahn-Teller Cu²⁺ (3d⁹) ion doped in the NiO, MgO, or ZnO crystal lattices having nearly perfect cubic symmetry is studied. The changes in the atomic electronic states that accompany formation of the solid solutions are revealed. The Ni_1-xCu_xO, Mg_1-xCu_xO, and Zn_1-xCu_xO solid solutions are synthesized and analyzed. The chemical shifts and widths of the CuK_α2, CuK_α1, and NiK_α1 lines are obtained. The copper atom shows a well-defined x dependence. The distinctions between the Cu states in the Ni-, Mg(Zn)-containing systems are found to be due to the distinctions in the electronic structures of the cations of a "host" lattice component. The chemical effects are found to be rather complicated. A possible role is revealed and estimations are made for the ratio between the relaxation times of the inner- and outer-shell electrons of the emitting atom, for the spin-polarized X-ray transitions, and for the partial effective atomic charges. The correlation between the obtained data and magnetic properties of solid solutions is established.