Comparing gold with an alkali metal, the "one outer electron" in gold is much less shielded from the nuclear charge -- therefore more tightly bound.
In an alkali metal, the outer electron surrounds a noble-gas core, e.g. sodium has a neon core and then that one
In gold the electrons immediately below the outer one do not have a noble gas configuration, they are less compact and thus they offer poorer shielding compared with an alkali metal. So the outer electron in gold is rather tightly bound.
However, the less compact electron structure in gold also means some "inner" electrons are potentially available for reaction. So if you do get gold to react, it may go beyond the