AbstractThe position, shape and the extended fine structure of the cobalt K absorption discontinuity have been studied in the pure metal and in its four chalcogenides, CoO, CoS, CoSe and CoTe, using a forty centimetre diameter bent crystal X‐ray spectrograph. It has been found that the discontinuity shifts towards the high energy side in the chalcogenides and that the chemical shift ΔEdepends upon the effective ionic charge on the absorbing atom. The fine structure within the main discontinuity is discussed on the basis of band structure and molecular orbital diagram, while the extended fine structure is interpreted on Lytle's theory. The results obtained throw light on the chemical bonding prevalent in these compoun