Re: Au has 1 val e- and filled inner shells, as does Ag & Cu. Why is Au inert?

Au, Ag, and Cu are often referred to as coinage metals or noble metals. None are inert. Even gold can be reacted with commonly available chemicals.

Gold will dissolve in aqua regia (a mixture of nitric acid and hydrochloric acids), and in basic solutions containing the cyanide ion.

See http://en.wikipedia.org/wiki/Gold for a basic overview of Gold compounds.

Gold dissolves in these systems because the gold cation forms stable complexes with chloride ions in aqua regia and cyanide ions in the cyanide systems.

The cyanide systems are used to leach traces of gold from ores and tailings. When the complexes are processed to recover the gold the cyanide wastes are a serious environmental hazard.

Gold has valence states ranging from -1 to +5. The most common are +1 and +3.