According with this discussion parts of my booklet "Gold electronic enigma, 1, 2 or 3" have been updated.
1st part to be updated:
2.Why they are noble?
Noble metals are a particular case of transition metals. Those with relativistic contraction (i.e. full 5d-band), comprising the heavy group, are even more unique.
Gold is found in nature as pure material. Pure silver and mercury result from their compounds by the action of light, heat...When the nuclei of metals become larger, the attraction between the nuclei and the electrons becomes stronger. Proceeding higher in the periodic table d-shells begin to be filled, s is already occupied or half of it. The electrons occupying the d-shells have higher energy than s-shell. They join in part s-electrons, forming the sea of electrons. Gold, silver and copper are different, having minimal hybridization amount, what results in 1) Lower melting points (softer metals). 2) Highest conductivities. This sea of electrons is the glue causing most transition metals to be so dense, hard and of high MP's. In contrast – metals without partly empty d-shell are softer, of lower MP's and higher atomic diameters. In case of reaction or conduction, most transition metals, d-electrons hybridized with s-electrons, make them sluggish, or directional rather than free, resulting in less conductivity and delayed reaction rates (passivation, kinetical delay). At one point, where the list of noble metals light group begins (Ru, Rh, Pd, Ag), said attraction and enveloping glue are combined in raising the oxidation potential thus protecting any particular electron from reacting. In the heavier group (Re, Os, Ir, Pt, Au, Hg), the relativistic contraction (p. 16) makes it still harder, stabilizes further the contracted atoms.
