[en] A question of participation of inner 6p-atomic orbitals in the formation of chemical bond and expansion of valency possibilities of actinides at the expense of it is discussed. The forecasting of new valency forms for actinides puts a question of their possible similarity with lantanides. It is shown that the similarity is of a ''cross'' character, and it is explained by cymbate change of excitation energy from fsup(n) to fsup(n-1)d-electron states. In the first half of lanthanides 4f-electron levels are more stable than in the second one, whereas in actinides in the first half 5f-levels are less stable than in the second one. Such similarity will be manifested in all properties, which are conditioned by partial participation in the formation of bonds of d-atomic orbitals. In the limiting case of ion configurations of fsup(n) tetrade effect should be manifested, which is conditioned by the fact that quantum numbers of complete orbital momentum are symmetric as to electron configurations of f₃(f₁₀) and f₄(f₁₁). It will be manifested in all the properties, which are determined by the diffusion of f-orbitals

[en] Short note. 1 tab

[en] Study of band structures of actinides from thorium to americium in hcp and bcc lattices is carried out by LCPW relativistic method corrugated potential with an account of relaxation skeleton states, and values of state densities on the Fermi level are obtained. Disagreement with experimental data by coefficient of γ-specific electron heat capacity for plutonium and neptunium is identified. Explanation of this fact, based on f-state localization due to Condo effect in these elements is proposed

[en] The band structure of metallic actinides from Am to Es is calculated by the LAPW method taking into account spin-orbit interaction and core relaxation. Densities of states, Fermi energies, densities of states at the Fermi level, and effective charges within MT-spheres are found for metals with face-centered-cubic (fcc) structures. The nature of the change of physicochemical properties along the series is discussed

[en] Calculations of zone structure of actinides from thorium to americium in FCC and BCC lattices were carried out by relativistic method with corrugated potential and with an account of skeleton state relaxation. Problems of f-state localization in metal americium are considered

[en] The problems associated with characteristic features of actinide elements are considered, viz. spatial configuration of nuclei in actinyl ions, possible existence of actinyl ions with angular structure, a relationship between the stability of actinyl ions and their geometry. Within the model of maximum overlap, it is shown that if in the actinide ion Ansup(Z+) there are closely spaced d- or s-levels in the electron configuration of the ground state, the dioxycation AnO₂²⁺ formed will be stable in the linear coordination. The geometry of actinyl systems is considered within the framework of efficient hybridization and from the viewpoint of electron-oscillation interaction

[en] The nature of correlation between redox potentials of actinide elements and absorption band frequencies in electron spectra of their complexes has been studied within the framework of quantum-chemical concept. The parameters affecting the redox potential and the scheme of molecular levels for octahedral complexes have been analyzed, and the absorption bands in electron spectra have been assigned. The value determining correlation is shown to be the energy of excitation into the valent state

[en] Stabilities of curium compounds with higher oxidation degrees of curium (Cmsup((5)), Cmsup((6)), Cmsup((7))) have been theoretically compared. Using the correlation between the energies of fsup(n)→fsup(n-d) d-transitions of curium atoms in the corresponding charge states with oxidation potentials (Cmsup((4-5))fsup(6)→fsup(5)dsup(1); Cmsup((5-6))fsup(5)→fsup(4)dsup(1); Cmsup((6-7)) fsup(4)→fsup(3)dsup(1)) it is found that Cmsup((7)) is unstable (Esup(0)(6-7)=2.7V) and Cmsup((6)) is to exist in the solutions: Esup(0)(5-6)=1.5V. At the same time Esup(0)(4-5)=17V, i.e. Cmsup((6)) is more stable than Cmsup((5))

[en] The influence of relativistic effects on the properties of heavy elements is shown. Using as an example transition d-elements, the role of relativistic effects in the stability of electron configuration of the ground state is studied, a comparison of chemical properties in series and periods is carried out. Special attention is paid to lanthanides and actinides. Importance of relativistic effects in the stability of valence forms, in changes of oxidation potentials, in existence of new oxidation rates is pointed out

[en] A model to calculate covalent effects in neptunium compounds with different ligands is suggested. A correlation between population of 5f-orbitals of neptunium and Moessbauer isomer shifts on ²³⁷Np nuclei is made. It is shown that in actinide fluorides AnF_x (An=U, Np, Pu and Am, x=3-6) covalent effects increase with an increase in oxidation state and decrease with an increase in actinide ordinal number, i. e. from U to Am. In neptunates populations of 5f-orbitals decrease, and those of 6d-orbitals increase with an increase in oxidation state, which corresponds to a higher delocalization of electrons and enhancing effects of (f-d)-hybridization. In neptunates (6) and (7) the higher is the deviation from octahedral symmetry, the greater are covalent effects. In compounds with neptunium-type bond the vacancy on the neptunyl bond in compound NaNp_1.5O₃ in terms of oxygen decreases its multiplicity and increases ionic character. On the whole, compounds with neptunyl bond are more covalent than neptunates. When compairing isovalent pairs NpO₆^z- and NpF_x, the inversion of ionicity is observed: oxygen compounds are more ionic than fluorides in lower oxidation states, and fluoride compounds - than fluorides in higher oxidation states