Kβ-to-Kα X-ray intensity ratios of Co and Cu have been measured in pure metals and in alloys of Co x Cu 1− x (x=0.8, 0.7, 0.6, 0.5, 0.4, 0.3 and 0.2) following excitation by 22.69keV X-rays from a 109 Cd radioactive point source. The valence-electronic configurations of these metals were determined by corporation of measured Kβ-to-Kα X-ray intensity ratios with the results of multiconfiguration Dirac–Fock (MCDF) calculation for various valence-electronic configurations. Valance electronic configurations of Co and Cu in alloys indicate significant differences with respect to the pure metals. Our analysis indicates that these differences arise from delocalization and/or charge transfer phenomena in alloys. Namely the observed change of the valence-electronic configurations of metals in alloys can be explained with the transfer of 3d electrons from one element to the other element and/or the rearrangement of electrons between 3d and 4s, 4p states of individual metal atoms.