AbstractWhen an atom is incorporated into a molecule or a crystal, its X‐ray spectrum undergoes characteristic changes, the study of which leads to important information on the nature of the chemical bonding and on the electronic structure in a substance. A number of examples are given to illustrate the possibilities of the X‐ray spectroscopy of bonded atoms. Special attention is given to the displacement of the Kα lines, from which conclusions can be drawn regarding the charge on a bonded atom, as well as to the investigation of the emission bands resulting from valence electron transitions, which yields information on the energy band structure of the solid. X‐ray spectroscopic studies on free molecules and theoretical work on the calculation of the molecular orbitals of simple molecules are finally re