Self-consistent field calculations are systematically carried out for common metals Cr, Mn, Fe, Co, Ni, Cu and Zn atoms and ions in order to understand the K-absorption edge and its chemical shift. It is found that: (1) a transition state introduced by Slater is very useful to predict the absorption edge energy; (2) there is a linear correlation between the absorption edge chemical shift and the cation charge of a crystal; and (3) the present model is applicable to ionic bonded crystals but is not very good for covalent ones. © 1991.