Monoatomic compounds are specifically compounds that are not diatomic. The term really only applies to gaseous compounds. For example, gaseous hydrogen has the formula H2, making is diatomic, while gaseous helium has the formula He, making it monoatomic.
Gold is a solid, and therefore has a crystal structure, making any discussion of it being monoatomic or diatomic meaningless.
The only way that gold could be 'monoatomic' is if it were in liquid or gas form, which in both cases would absolutely not be a 'white powdered' substance, but would rather be extremely hot, extremely toxic molten or vaporised metal.
Finally, compounds that do not exist monoatomically in nature generally cannot exist monoatomically otherwise. A compound with the formula H, for example, cannot exist for any longer than a few seconds, because it will necessarily bond with something.
In conclusion, 'monoatomic gold' is nonsense.