I am just wondering about the theoretical basis of the red colour of copper metal.
I have learnt that the yellow colour of gold (Au) is due to significant relativistic effect and resulting in contracted 5d and 6s shells and the transition from 6s --> 5d now falls within the visible region. (pls correct me if I am wrong or inaccurate)
This only affects heavy elements, so copper cannot be red due to this same reason.
Does it have a transition that absorb blue/green region? which one?
Also, it is interesting that caesium metal (Cs) appears as a golden coloured metal, does anyone know whether this golden colour is due to a very minor oxidation of the metal or whether there is a physical basis for this colour?
Very interested to learn more, Many thanks for any replies.
About gold, yes you are correct, relativistic effects reduce the transition 5d-6s.
However, is not Cu-4s transition already of the order of 2-3 eV? I have not checked this!
I say because i am seeing now that dissociation energies for dimers are approx. (eV)
Relativistics effects for 6s1
increase the energy breaking the nonrelativistic tendency 2 -> 1.6 -> 1.
For trimers, Au3
are still more similar with Ag rather different.
I think that Cu color may be normal and the only Au color is abnormal due to relativistic effects.
I continue searching information