In the electrode potential series, only copper have positive value for electrode potential because copper has lower tendency than hydrogen to form ions. So, if standard hydrogen electrode (E‌Cell ‌=0) is connected to copper half-cell, the copper with be relatively less negative or less number of electrons. ‌E(Cu2+∕Cu)∘=+0.34V;‌‌E(Fe2+∕Fe)∘=−0.41V ‌ECo∘∕2∕Co∘=−0.28V;‌‌E(Zn2+∕Zn)∘=−0.76V ∴ Electrode potential of CuECu+2∕Cu∘ show positive value.