The metal from the first transition series having positive \(E_{M^{2+}/M}^0\) value:

Cr V Cu Ni

Cu

In the electrochemical series, Cu is below hydrogen. Hence, it has a positive value of standard reduction potential \(E_{M^{2+}/M}^0\). The standard reduction potentials are given below: Cr (Z = 24) = − 0.91 V V (Z= 23) = −1.18 V Cu (Z=29) = +0.34 V Ni (Z= 30) = −0.76 V