Valency: The valency of an atom is defined as the number of electrons gained or lost from the valence shell by an atom to attain noble gas electronic configuration.
Gold belongs to the d-block element of group 11 and 6th period.
The atomic number of Gold(Au)=79
The electronic configuration of Gold is
From electronic configuration, we concluded that 1 electron is present in the outermost valence shell which can be removed easily to attain the stable configuration.