jats:titleAbstract</jats:title>jats:pThe nature of the chemical bond in UOjats:sub2</jats:sub> was analyzed taking into account the X‐ray photoelectron spectroscopy (XPS) structure parameters of the valence and core electrons, as well as the relativistic discrete variation electronic structure calculation results for this oxide. The ionic/covalent nature of the chemical bond was determined for the UOjats:sub8</jats:sub> (Djats:sub4h</jats:sub>) cluster, reflecting uranium's close environment in UOjats:sub2</jats:sub>, and the Ujats:sub13</jats:sub>Ojats:sub56</jats:sub> and Ujats:sub63</jats:sub>Ojats:sub216</jats:sub> clusters, reflecting the bulk of solid uranium dioxide. The bar graph of the theoretical valence band (from 0 to ~35 eV) of XPS spectrum was built such that it was in satisfactory agreement with the experimental spectrum of a UOjats:sub2</jats:sub> single crystalline thin film. It was shown that unlike the crystal field theory results, the covalence effects in UOjats:sub2</jats:sub> are significant due to the strong overlap of the U 6p and U 5f atomic orbitals with the ligand orbitals, in addition to the U 6d atomic orbital (AO). A quantitative molecular orbital (MO) scheme for UOjats:sub2</jats:sub> was built. The contribution of the MO electrons to the chemical bond covalence component was evaluated on the basis of the bond population values. It was found that the electrons of inner valence molecular orbitals (IVMO) weaken the chemical bond formed by the electrons of outer valence molecular orbitals (OVMO) by 32% in UOjats:sub8</jats:sub> and by 25% in Ujats:sub63</jats:sub>Ojats:sub216</jats:sub>.</jats:p>