Metallradien, Ionenradien und Wertigkeiten fester metallischer Elemente / Metallradien, Ionenradien und Wertigkeiten fester metallischer Elemente

Metallic radii rm are correlated with the ionic radii ri by linear relationships. For groups 1 up to 7 as well as for AI, Ga, In, Tl, Sn, and Pb the ionic radii refer to the maximum valences (oxidation states) as known from compounds according to rm ≈ 1.16 • (ri + 0.64) [Å], For groups 8 up to 12, rm ≈ 0.48 · (ri + 2.26) [Å] with valences W = 14 -G (G = group number). These valences are considered regular (Wr). For groups 1 up to 12, they obey the equation Wr = 7 -[G -71]. According to this equation all outer s electrons and the unpaired d electrons should be involved in chemical bonding, i.e. in the cohesion of the element in the solid state. From the melting temperatures and the atomic volumes it is concluded, however, that only 19 out of the 30 d-block elements have regular valences, namely the elements of groups 3, 5, 6, 10, 11 as well as Os, Ir, Zn, Cd, and possibly Ru. All of the non-regular valences are lower than the regular ones. Four of them are integers: Mn 3; Fe, Co 4; Re 6.