[FredZarguna]

Oh geez. You are 100% correct! I had forgotten that the Dirac equation leads to a completely different aufbau than the Schrodinger/Heisenberg one. In addition to the Lanthanide contraction caused by relativistic effects (at least I remembered that part correctly) in Au there is an additional contraction of the 6s orbital so the 5d -> 6s transition (into the conduction band) is so small it absorbs in the blue, rather than UV and higher as is the case of the bound electron orbitals in most metals. Have a go: http://voh.chem.ucla.edu/vohtar/fall02/classes/172/pdf/172rpint.pdf.

A more lay accessible treatment is here: http://www.fourmilab.ch/documents/golden_glow/. Which has some errors (the transition is 4d->5s in Ag, not Au) but omits the complexity of band theory altogether; and seems "correct enough."

Now, that still doesn't explain Cu, and I sure don't remember any more. No time tonight, though.

Thanks. That was fun.

[thecodont]

Thanks for the fun “golden glow” link from Fermilab! I have a “Periodic Table of the Elements” calendar for 2012, and December features — what else — Au, gold.

[grey_whiskers]

Thanks for the links. (Sound of grey_whiskers purring LOUDLY.)

I owe you a beer!

g_w