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Electronic Structure of Gold

Electronic structure of gold, the high corrosion resistance of gold is a consequence of its first ionization potential being 9.2 eV,which is high compared to those of, for example, silver and copper, at 7.6 and 7.7 eV, respectively. This results in such a large barrier to oxidation that elemental gold is ordinarily free of an oxide coating. Gold has the electronic configuration [Xe]4f145d106s1. In this configuration the 4f electrons underscreen the 5d and the 6s,p electrons from the nuclear charge, resulting in an effect analogous to lanthanide contraction.

The lanthanide contraction causes the atomic radius of the lanthanides to decrease across the period as the quality of the shielding per electron decreases; in the 5d metal series this effect gives similar lattice constants to the 4d metals. For some years the stability of the Au2 dimer and the reduced lattice constant in bulk gold compared to silver were attributed to a similar contraction [7]. However, gold is in a unique spot on the periodic table where the effects of the lanthanide contraction are also superimposed on the onset of relativistic effects.

The latter become increasingly important for the heavier elements because as the atomic number increases,the velocity of the 1s electrons approaches the speed of light. This causes these electrons to increase in mass and so their orbital contracts toward the nucleus. To compensate, the higher s and p orbitals, which also have significant electron density in the vicinity of the nucleus, also contract, resulting finally in the outermost 6s and 6p orbitals being smaller than they would otherwise have been without relativistic effects.