Relationship between some properties of the transition metals, characterizing their interatomic bond strength, and their electronic structure

Summary

The change of some physical and thermodynamic properties of the transition metals is analyzed in relationship to their position in the periodic system of elements. On this basis it is shown that the increase of interatomic bond strength in each subgroup of the transition metals with increasing atomic number is largely due to the overlapping of the electron clouds of ions.

It is necessary to distinguish two groups of physical properties of the transition metals, which characterize interatomic bond strength in the latter. The first group of properties characterizes the energy required for the full rupture of bonds in the crystal lattice and the second — bond deformability. The first group of properties includes the energy of sublimation and the melting point, and the second — the modulus of elasticity, the coefficient of compressibility, atomic diameters, and mean square displacements.

The fact that bond deformability decreases in the crystal lattices of the first metals of group VIII compared with the metals of group VI and in the lattices of the copper-group metals compared with the titanium-group metals, although the energy required for bond rupture decreases, is attributed to increased overlapping of the electron clouds of ions.

In metals, it is necessary to differentiate between the valence which characterizes the overlapping of the electron shells of ions (Pauling valence) and the valence due to collectivized electrons (Hume-Rothery valence).