2592.     PAULING, L.  Nature of the Interatomic Forces in Metals.  I.  Phys. Rev., vol. 54, 1938, pp. 899-904; Chem. Abs., vol. 33, 1939, p. 1205.

        It has been generally assumed that in the transition elements (Fe, Co, Ni, Cu) the 3d shell is filled with 10 electrons or is nearly filled, and that the d electrons make no significant contribution to the cohesive force in metals.  Evidence is now presented showing that about half of the d orbitals (2.56 of the total of 5) are involved in bond formation, and that the number of covalent bonds resonating among the available interatomic positions increases from 1 to nearly 6 in the sequence K, Ca, Sc, Ti, V, Cr; remains nearly constant from Cr to Ni; and begins to decrease with Cu.  The remaining 2.44 d orbitals, with very small interatomic overlapping, are occupied by nonbinding electrons, which are mainly responsible for the ferromagnetic and paramagnetic properties of the metals.  This point of view provides a qualitative explanation of many properties of the transition metals, such as interatomic distance, characteristic temperature, hardness, compressibility, and coefficient of thermal expansion, and it accounts satisfactorily for the observed values of the atomic saturation magnetic moments of the ferromagnetic elements, Fe, Co, Ni, and their alloys.  It also provides a reason for the occurrence of the positive exchange integrals, which give rise to ferromagnetism.