Answer is: copper (Cu).
Gold (Au) and silver (Ag) are noble metals and fall into the transitional metal family on the periodic table in group number 11.
Group 11 is also known as the coinage metals, due to their former usage.
Copper, silver and gold all occur naturally in elemental form.
Copper has atomic number 29, it has 29 protons and 29 electrons.
Electron configuration of copper atom: ₂₉Cu [Ar] 3d¹⁰ 4s¹.
Copper (Cu) is higher in activity series than silver and gold, so copper lose electron and silver gain electrons.